The AAO/UKST SuperCOSMOS Hα survey
Identifieur interne : 002797 ( Istex/Corpus ); précédent : 002796; suivant : 002798The AAO/UKST SuperCOSMOS Hα survey
Auteurs : Quentin A. Parker ; S. Phillipps ; M. J. Pierce ; M. Hartley ; N. C. Hambly ; M. A. Read ; H. T. Macgillivray ; S. B. Tritton ; C. P. Cass ; R. D. Cannon ; M. Cohen ; J. E. Drew ; D. J. Frew ; E. Hopewell ; S. Mader ; D. F. Malin ; M. R. W. Masheder ; D. H. Morgan ; R. A. H. Morris ; D. Russeil ; K. S. Russell ; R. N. F. WalkerSource :
- Monthly Notices of the Royal Astronomical Society [ 0035-8711 ] ; 2005-09-11.
English descriptors
- KwdEn :
Abstract
The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N ii] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.
Url:
DOI: 10.1111/j.1365-2966.2005.09350.x
Links to Exploration step
ISTEX:D6276BED7D62FB067443F2193817ECCDA3997AC7Le document en format XML
<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>The AAO/UKST SuperCOSMOS Hα survey</title><author><name sortKey="Parker, Quentin A" sort="Parker, Quentin A" uniqKey="Parker Q" first="Quentin A." last="Parker">Quentin A. Parker</name><affiliation><mods:affiliation>Macquarie University, Sydney, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: qap@ics.mq.edu.au</mods:affiliation></affiliation><affiliation><mods:affiliation></mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: qap@ics.mq.edu.au</mods:affiliation></affiliation></author><author><name sortKey="Phillipps, S" sort="Phillipps, S" uniqKey="Phillipps S" first="S." last="Phillipps">S. Phillipps</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Pierce, M J" sort="Pierce, M J" uniqKey="Pierce M" first="M. J." last="Pierce">M. J. Pierce</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Hartley, M" sort="Hartley, M" uniqKey="Hartley M" first="M." last="Hartley">M. Hartley</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Hambly, N C" sort="Hambly, N C" uniqKey="Hambly N" first="N. C." last="Hambly">N. C. Hambly</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Read, M A" sort="Read, M A" uniqKey="Read M" first="M. A." last="Read">M. A. Read</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Macgillivray, H T" sort="Macgillivray, H T" uniqKey="Macgillivray H" first="H. T." last="Macgillivray">H. T. Macgillivray</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Tritton, S B" sort="Tritton, S B" uniqKey="Tritton S" first="S. B." last="Tritton">S. B. Tritton</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Cass, C P" sort="Cass, C P" uniqKey="Cass C" first="C. P." last="Cass">C. P. Cass</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Cannon, R D" sort="Cannon, R D" uniqKey="Cannon R" first="R. D." last="Cannon">R. D. Cannon</name><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Cohen, M" sort="Cohen, M" uniqKey="Cohen M" first="M." last="Cohen">M. Cohen</name><affiliation><mods:affiliation>UC, Berkeley, USA</mods:affiliation></affiliation></author><author><name sortKey="Drew, J E" sort="Drew, J E" uniqKey="Drew J" first="J. E." last="Drew">J. E. Drew</name><affiliation><mods:affiliation>Imperial College, London</mods:affiliation></affiliation></author><author><name sortKey="Frew, D J" sort="Frew, D J" uniqKey="Frew D" first="D. J." last="Frew">D. J. Frew</name><affiliation><mods:affiliation>Macquarie University, Sydney, Australia</mods:affiliation></affiliation></author><author><name sortKey="Hopewell, E" sort="Hopewell, E" uniqKey="Hopewell E" first="E." last="Hopewell">E. Hopewell</name><affiliation><mods:affiliation>Imperial College, London</mods:affiliation></affiliation></author><author><name sortKey="Mader, S" sort="Mader, S" uniqKey="Mader S" first="S." last="Mader">S. Mader</name><affiliation><mods:affiliation>Australia Telescope National Facility, Parkes, Australia</mods:affiliation></affiliation></author><author><name sortKey="Malin, D F" sort="Malin, D F" uniqKey="Malin D" first="D. F." last="Malin">D. F. Malin</name><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Masheder, M R W" sort="Masheder, M R W" uniqKey="Masheder M" first="M. R. W." last="Masheder">M. R. W. Masheder</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Morgan, D H" sort="Morgan, D H" uniqKey="Morgan D" first="D. H." last="Morgan">D. H. Morgan</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Morris, R A H" sort="Morris, R A H" uniqKey="Morris R" first="R. A. H." last="Morris">R. A. H. Morris</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Russeil, D" sort="Russeil, D" uniqKey="Russeil D" first="D." last="Russeil">D. Russeil</name><affiliation><mods:affiliation>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</mods:affiliation></affiliation></author><author><name sortKey="Russell, K S" sort="Russell, K S" uniqKey="Russell K" first="K. S." last="Russell">K. S. Russell</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Walker, R N F" sort="Walker, R N F" uniqKey="Walker R" first="R. N. F." last="Walker">R. N. F. Walker</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:D6276BED7D62FB067443F2193817ECCDA3997AC7</idno><date when="2005" year="2005">2005</date><idno type="doi">10.1111/j.1365-2966.2005.09350.x</idno><idno type="url">https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">002797</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">002797</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">The AAO/UKST SuperCOSMOS Hα survey</title><author><name sortKey="Parker, Quentin A" sort="Parker, Quentin A" uniqKey="Parker Q" first="Quentin A." last="Parker">Quentin A. Parker</name><affiliation><mods:affiliation>Macquarie University, Sydney, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: qap@ics.mq.edu.au</mods:affiliation></affiliation><affiliation><mods:affiliation></mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: qap@ics.mq.edu.au</mods:affiliation></affiliation></author><author><name sortKey="Phillipps, S" sort="Phillipps, S" uniqKey="Phillipps S" first="S." last="Phillipps">S. Phillipps</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Pierce, M J" sort="Pierce, M J" uniqKey="Pierce M" first="M. J." last="Pierce">M. J. Pierce</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Hartley, M" sort="Hartley, M" uniqKey="Hartley M" first="M." last="Hartley">M. Hartley</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Hambly, N C" sort="Hambly, N C" uniqKey="Hambly N" first="N. C." last="Hambly">N. C. Hambly</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Read, M A" sort="Read, M A" uniqKey="Read M" first="M. A." last="Read">M. A. Read</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Macgillivray, H T" sort="Macgillivray, H T" uniqKey="Macgillivray H" first="H. T." last="Macgillivray">H. T. Macgillivray</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Tritton, S B" sort="Tritton, S B" uniqKey="Tritton S" first="S. B." last="Tritton">S. B. Tritton</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Cass, C P" sort="Cass, C P" uniqKey="Cass C" first="C. P." last="Cass">C. P. Cass</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Cannon, R D" sort="Cannon, R D" uniqKey="Cannon R" first="R. D." last="Cannon">R. D. Cannon</name><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Cohen, M" sort="Cohen, M" uniqKey="Cohen M" first="M." last="Cohen">M. Cohen</name><affiliation><mods:affiliation>UC, Berkeley, USA</mods:affiliation></affiliation></author><author><name sortKey="Drew, J E" sort="Drew, J E" uniqKey="Drew J" first="J. E." last="Drew">J. E. Drew</name><affiliation><mods:affiliation>Imperial College, London</mods:affiliation></affiliation></author><author><name sortKey="Frew, D J" sort="Frew, D J" uniqKey="Frew D" first="D. J." last="Frew">D. J. Frew</name><affiliation><mods:affiliation>Macquarie University, Sydney, Australia</mods:affiliation></affiliation></author><author><name sortKey="Hopewell, E" sort="Hopewell, E" uniqKey="Hopewell E" first="E." last="Hopewell">E. Hopewell</name><affiliation><mods:affiliation>Imperial College, London</mods:affiliation></affiliation></author><author><name sortKey="Mader, S" sort="Mader, S" uniqKey="Mader S" first="S." last="Mader">S. Mader</name><affiliation><mods:affiliation>Australia Telescope National Facility, Parkes, Australia</mods:affiliation></affiliation></author><author><name sortKey="Malin, D F" sort="Malin, D F" uniqKey="Malin D" first="D. F." last="Malin">D. F. Malin</name><affiliation><mods:affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Masheder, M R W" sort="Masheder, M R W" uniqKey="Masheder M" first="M. R. W." last="Masheder">M. R. W. Masheder</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Morgan, D H" sort="Morgan, D H" uniqKey="Morgan D" first="D. H." last="Morgan">D. H. Morgan</name><affiliation><mods:affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</mods:affiliation></affiliation></author><author><name sortKey="Morris, R A H" sort="Morris, R A H" uniqKey="Morris R" first="R. A. H." last="Morris">R. A. H. Morris</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author><author><name sortKey="Russeil, D" sort="Russeil, D" uniqKey="Russeil D" first="D." last="Russeil">D. Russeil</name><affiliation><mods:affiliation>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</mods:affiliation></affiliation></author><author><name sortKey="Russell, K S" sort="Russell, K S" uniqKey="Russell K" first="K. S." last="Russell">K. S. Russell</name><affiliation><mods:affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</mods:affiliation></affiliation></author><author><name sortKey="Walker, R N F" sort="Walker, R N F" uniqKey="Walker R" first="R. N. F." last="Walker">R. N. F. Walker</name><affiliation><mods:affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Monthly Notices of the Royal Astronomical Society</title><title level="j" type="abbrev">Mon. Not. R. Astron. Soc.</title><idno type="ISSN">0035-8711</idno><idno type="eISSN">1365-2966</idno><imprint><publisher>Blackwell Science Ltd</publisher><pubPlace>Oxford, UK</pubPlace><date type="published" when="2005-09-11">2005-09-11</date><biblScope unit="volume">362</biblScope><biblScope unit="issue">2</biblScope><biblScope unit="page" from="689">689</biblScope><biblScope unit="page" to="710">710</biblScope></imprint><idno type="ISSN">0035-8711</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0035-8711</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>astronomical data bases: miscellaneous</term><term>catalogues</term><term>photometry</term><term>stars: emission line</term><term>surveys</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract">The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N ii] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.</div></front></TEI><istex><corpusName>oup</corpusName><author><json:item><name>Quentin A. Parker</name><affiliations><json:string>Macquarie University, Sydney, Australia</json:string><json:string>Anglo-Australian Observatory, Epping, New South Wales, Australia</json:string><json:string>E-mail: qap@ics.mq.edu.au</json:string><json:null></json:null><json:string>E-mail: qap@ics.mq.edu.au</json:string></affiliations></json:item><json:item><name>S. Phillipps</name><affiliations><json:string>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</json:string></affiliations></json:item><json:item><name>M. J. Pierce</name><affiliations><json:string>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</json:string></affiliations></json:item><json:item><name>M. Hartley</name><affiliations><json:string>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</json:string></affiliations></json:item><json:item><name>N. C. Hambly</name><affiliations><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string></affiliations></json:item><json:item><name>M. A. Read</name><affiliations><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string></affiliations></json:item><json:item><name>H. T. MacGillivray</name><affiliations><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string></affiliations></json:item><json:item><name>S. B. Tritton</name><affiliations><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string></affiliations></json:item><json:item><name>C. P. Cass</name><affiliations><json:string>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</json:string></affiliations></json:item><json:item><name>R. D. Cannon</name><affiliations><json:string>Anglo-Australian Observatory, Epping, New South Wales, Australia</json:string></affiliations></json:item><json:item><name>M. Cohen</name><affiliations><json:string>UC, Berkeley, USA</json:string></affiliations></json:item><json:item><name>J. E. Drew</name><affiliations><json:string>Imperial College, London</json:string></affiliations></json:item><json:item><name>D. J. Frew</name><affiliations><json:string>Macquarie University, Sydney, Australia</json:string></affiliations></json:item><json:item><name>E. Hopewell</name><affiliations><json:string>Imperial College, London</json:string></affiliations></json:item><json:item><name>S. Mader</name><affiliations><json:string>Australia Telescope National Facility, Parkes, Australia</json:string></affiliations></json:item><json:item><name>D. F. Malin</name><affiliations><json:string>Anglo-Australian Observatory, Epping, New South Wales, Australia</json:string></affiliations></json:item><json:item><name>M. R. W. Masheder</name><affiliations><json:string>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</json:string></affiliations></json:item><json:item><name>D. H. Morgan</name><affiliations><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string></affiliations></json:item><json:item><name>R. A. H. Morris</name><affiliations><json:string>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</json:string></affiliations></json:item><json:item><name>D. Russeil</name><affiliations><json:string>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</json:string></affiliations></json:item><json:item><name>K. S. Russell</name><affiliations><json:string>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</json:string></affiliations></json:item><json:item><name>R. N. F. Walker</name><affiliations><json:string>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</json:string></affiliations></json:item></author><subject><json:item><value>astronomical data bases: miscellaneous</value></json:item><json:item><value>catalogues</value></json:item><json:item><value>surveys</value></json:item><json:item><value>stars: emission line</value></json:item><json:item><value>photometry</value></json:item></subject><arkIstex>ark:/67375/HXZ-DMNVV866-V</arkIstex><language><json:string>unknown</json:string></language><originalGenre><json:string>research-article</json:string></originalGenre><abstract>The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N ii] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.</abstract><qualityIndicators><score>9.592</score><pdfWordCount>15944</pdfWordCount><pdfCharCount>87051</pdfCharCount><pdfVersion>1.4</pdfVersion><pdfPageCount>22</pdfPageCount><pdfPageSize>612 x 792 pts (letter)</pdfPageSize><refBibsNative>true</refBibsNative><abstractWordCount>216</abstractWordCount><abstractCharCount>1414</abstractCharCount><keywordCount>5</keywordCount></qualityIndicators><title>The AAO/UKST SuperCOSMOS Hα survey</title><genre><json:string>research-article</json:string></genre><host><title>Monthly Notices of the Royal Astronomical Society</title><language><json:string>unknown</json:string></language><issn><json:string>0035-8711</json:string></issn><eissn><json:string>1365-2966</json:string></eissn><publisherId><json:string>mnras</json:string></publisherId><volume>362</volume><issue>2</issue><pages><first>689</first><last>710</last></pages><genre><json:string>journal</json:string></genre></host><namedEntities><unitex><date><json:string>2005</json:string><json:string>1997</json:string><json:string>1990s</json:string><json:string>1000</json:string><json:string>17s</json:string><json:string>2002</json:string><json:string>1970s</json:string><json:string>2003</json:string></date><geogName></geogName><orgName><json:string>National Science Foundation</json:string><json:string>Industrial Research Organization</json:string><json:string>University of Edinburgh</json:string><json:string>World Co</json:string><json:string>Engineering Research Council</json:string><json:string>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</json:string><json:string>UKST</json:string><json:string>Institute for Astronomy Edinburgh</json:string><json:string>Cerro Tololo Inter-American Observatory</json:string><json:string>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</json:string><json:string>Kodak publication P-315</json:string><json:string>Australia Group, University of Bristol, Tyndall Avenue, Bristol</json:string><json:string>Australia Telescope National Facility, Parkes, Australia</json:string><json:string>Macquarie University</json:string><json:string>CTIO</json:string><json:string>CSIRO</json:string><json:string>National Measurement Laboratory</json:string><json:string>Astronomy Research Council</json:string><json:string>UK Schmidt Telescope</json:string><json:string>AAO</json:string></orgName><orgName_funder><json:string>AAO</json:string></orgName_funder><orgName_provider></orgName_provider><persName><json:string>Fred Watson</json:string><json:string>Ann Savage</json:string><json:string>Sky Survey</json:string><json:string>C. Hambly</json:string><json:string>Virginia Tech</json:string><json:string>D. J. Frew</json:string><json:string>Meaburn</json:string><json:string>S. Tritton</json:string><json:string>John Meaburn</json:string><json:string>A. Read</json:string><json:string>Newton Telescope</json:string><json:string>D. F. Malin</json:string><json:string>Quentin A. Parker</json:string><json:string>E. Hopewell</json:string><json:string>La Palma</json:string><json:string>Sky Surveys</json:string><json:string>Brian Boyle</json:string><json:string>Russell Cannon</json:string><json:string>J. Pierce</json:string><json:string>The</json:string><json:string>M. Hartley</json:string><json:string>P. Cass</json:string><json:string>R. W. Masheder</json:string><json:string>D. Russeil</json:string><json:string>S. Mader</json:string><json:string>M. Read</json:string><json:string>R. N. F. Walker</json:string><json:string>D. H. Morgan</json:string><json:string>D. Cannon</json:string><json:string>Star</json:string><json:string>E. Drew</json:string><json:string>S. B. Tritton</json:string><json:string>A. H. Morris</json:string><json:string>H. T. MacGillivray</json:string><json:string>S. Phillipps</json:string></persName><placeName><json:string>Australia</json:string><json:string>UK</json:string><json:string>Edinburgh</json:string><json:string>Strasbourg</json:string><json:string>Berkeley</json:string><json:string>France</json:string><json:string>Marseille</json:string><json:string>Sydney</json:string></placeName><ref_url><json:string>http://astro.ic.ac.uk/Research/Halpha/North/</json:string><json:string>http://heasarc.gsfc.nasa</json:string><json:string>http://www-wfau.roe.ac.uk/sss/halpha</json:string><json:string>http://www.astro.wisc.edu/wham</json:string><json:string>http://www-wfau.roe.ac.uk/sss/halpha/</json:string><json:string>http://amundsen.swarthmore.edu/SHASSA/</json:string><json:string>http://amundsen.swarthmore.edu/SHASSA</json:string><json:string>http://www.phys.vt.edu/halpha</json:string><json:string>http://www.zoomify.com</json:string><json:string>http://surveys.roe.ac.uk/ssa/hablock/hafull.html</json:string><json:string>http://www-wfau.roe</json:string></ref_url><ref_bibl><json:string>Parker & Malin 1999</json:string><json:string>Dennison et al. (1998)</json:string><json:string>Kennicutt 1992</json:string><json:string>Q. A. Parker et al.</json:string><json:string>Morgan, Parker & Russeil 2001</json:string><json:string>Haffner et al. 2003</json:string><json:string>Pierce 2005</json:string><json:string>Hambly et al. (2001b)</json:string><json:string>Parker et al. 2003</json:string><json:string>Bond et al. (2001)</json:string><json:string>Phillipps & Parker 1993</json:string><json:string>Zacharias et al. 2004</json:string><json:string>Elmegreen & Lada 1977</json:string><json:string>Jarrett et al. 2000</json:string><json:string>Storkey et al. (2004)</json:string><json:string>Gaustad et al. 2001</json:string><json:string>Boyle, Shanks & Croom 1995</json:string><json:string>Meaburn 1980</json:string><json:string>Cohen, Parker & Chapman 2005</json:string><json:string>Tenorio-Tagle & Palous 1987</json:string><json:string>Schlegel, Finkbeiner & Davis 1998</json:string><json:string>Hopewell et al. 2005</json:string><json:string>Kodak 1987</json:string><json:string>Morgan, Parker & Cohen 2003</json:string><json:string>Davies et al. 1976</json:string><json:string>Keller et al. (2001)</json:string><json:string>Hopewell et al. (2005)</json:string><json:string>Hambly et al. (2001c)</json:string><json:string>Parker (2001)</json:string><json:string>Hog et al. 2000</json:string><json:string>Buxton et al. 1998</json:string><json:string>April 1997</json:string><json:string>Hambly et al. 2001b</json:string><json:string>Croom et al. 1999</json:string><json:string>Drew et al. (2004)</json:string><json:string>Green et al. 1999</json:string><json:string>Osterbrock 1989</json:string><json:string>Hambly et al. 1998</json:string><json:string>Nossal et al. (2001)</json:string><json:string>Meaburn & White 1982</json:string><json:string>Russeil et al. 1997, 1998</json:string><json:string>1998, 2003</json:string><json:string>[3]</json:string><json:string>Parker, Frew & Stupar 2004</json:string><json:string>Pierce et al.</json:string><json:string>Boyle et al. (1995)</json:string><json:string>Russeil et al. 2005</json:string><json:string>Beard, MacGillivray & Thanisch 1990</json:string><json:string>Miller et al. 1992</json:string><json:string>Peyaud, Parker & Acker 2003</json:string><json:string>Pickering 1890</json:string><json:string>Dennison et al. 1998</json:string><json:string>Rizzo & Arnal 1998</json:string><json:string>Drew et al. (2005)</json:string><json:string>Croom et al. (1999)</json:string><json:string>Gum 1952</json:string><json:string>Price et al. 2001</json:string><json:string>Frew, Parker & Russeil 2005</json:string><json:string>Georgelin et al. 2000</json:string><json:string>Pierce et al. 2004</json:string><json:string>Hafner et al. (2003)</json:string><json:string>Arrowsmith & Parker 2001</json:string><json:string>Hambly et al. (2001)</json:string><json:string>Watson 1984</json:string><json:string>Parker et al. 2003, 2005</json:string><json:string>Gerola & Seiden 1978</json:string><json:string>Mader et al. (1999)</json:string><json:string>Finkbeiner (2003)</json:string><json:string>Parker & Morgan 2003</json:string><json:string>Stupar et al.</json:string><json:string>Hambly et al. (2001a)</json:string><json:string>Bland-Hawthorn et al. 1998</json:string><json:string>Parker et al.</json:string><json:string>Mel’Nik & Efremov 1995</json:string><json:string>Parker et al. 2003b, 2005</json:string><json:string>Schlegel et al. 1998</json:string><json:string>Gaustad et al. (2001)</json:string><json:string>1955, 1956</json:string><json:string>Cohen et al. (2002)</json:string></ref_bibl><bibl></bibl></unitex></namedEntities><ark><json:string>ark:/67375/HXZ-DMNVV866-V</json:string></ark><categories><wos><json:string>science</json:string><json:string>astronomy & astrophysics</json:string></wos><scienceMetrix><json:string>natural sciences</json:string><json:string>physics & astronomy</json:string><json:string>astronomy & astrophysics</json:string></scienceMetrix><scopus><json:string>1 - Physical Sciences</json:string><json:string>2 - Earth and Planetary Sciences</json:string><json:string>3 - Space and Planetary Science</json:string><json:string>1 - Physical Sciences</json:string><json:string>2 - Physics and Astronomy</json:string><json:string>3 - Astronomy and Astrophysics</json:string></scopus><inist><json:string>sciences appliquees, technologies et medecines</json:string><json:string>sciences exactes et technologie</json:string><json:string>terre, ocean, espace</json:string><json:string>astronomie</json:string></inist></categories><publicationDate>2005</publicationDate><copyrightDate>2005</copyrightDate><doi><json:string>10.1111/j.1365-2966.2005.09350.x</json:string></doi><id>D6276BED7D62FB067443F2193817ECCDA3997AC7</id><score>1</score><fulltext><json:item><extension>pdf</extension><original>true</original><mimetype>application/pdf</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/fulltext/pdf</uri></json:item><json:item><extension>zip</extension><original>false</original><mimetype>application/zip</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a">The AAO/UKST SuperCOSMOS Hα survey</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher scheme="https://publisher-list.data.istex.fr">Blackwell Science Ltd</publisher><pubPlace>Oxford, UK</pubPlace><availability><licence><p>© 2005 RAS</p></licence><p scheme="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-GTWS0RDP-M">oup</p></availability><date>2005</date></publicationStmt><notesStmt><note type="research-article" scheme="https://content-type.data.istex.fr/ark:/67375/XTP-1JC4F85T-7">research-article</note><note type="journal" scheme="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</note></notesStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a">The AAO/UKST SuperCOSMOS Hα survey</title><author xml:id="author-0000" corresp="yes"><persName><forename type="first">Quentin A.</forename><surname>Parker</surname></persName><email>qap@ics.mq.edu.au</email><email>qap@ics.mq.edu.au</email><affiliation>Macquarie University, Sydney, Australia</affiliation><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation><affiliation></affiliation></author><author xml:id="author-0001"><persName><forename type="first">S.</forename><surname>Phillipps</surname></persName><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation></author><author xml:id="author-0002"><persName><forename type="first">M. J.</forename><surname>Pierce</surname></persName><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation></author><author xml:id="author-0003"><persName><forename type="first">M.</forename><surname>Hartley</surname></persName><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation></author><author xml:id="author-0004"><persName><forename type="first">N. C.</forename><surname>Hambly</surname></persName><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation></author><author xml:id="author-0005"><persName><forename type="first">M. A.</forename><surname>Read</surname></persName><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation></author><author xml:id="author-0006"><persName><forename type="first">H. T.</forename><surname>MacGillivray</surname></persName><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation></author><author xml:id="author-0007"><persName><forename type="first">S. B.</forename><surname>Tritton</surname></persName><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation></author><author xml:id="author-0008"><persName><forename type="first">C. P.</forename><surname>Cass</surname></persName><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation></author><author xml:id="author-0009"><persName><forename type="first">R. D.</forename><surname>Cannon</surname></persName><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation></author><author xml:id="author-0010"><persName><forename type="first">M.</forename><surname>Cohen</surname></persName><affiliation>UC, Berkeley, USA</affiliation></author><author xml:id="author-0011"><persName><forename type="first">J. E.</forename><surname>Drew</surname></persName><affiliation>Imperial College, London</affiliation></author><author xml:id="author-0012"><persName><forename type="first">D. J.</forename><surname>Frew</surname></persName><affiliation>Macquarie University, Sydney, Australia</affiliation></author><author xml:id="author-0013"><persName><forename type="first">E.</forename><surname>Hopewell</surname></persName><affiliation>Imperial College, London</affiliation></author><author xml:id="author-0014"><persName><forename type="first">S.</forename><surname>Mader</surname></persName><affiliation>Australia Telescope National Facility, Parkes, Australia</affiliation></author><author xml:id="author-0015"><persName><forename type="first">D. F.</forename><surname>Malin</surname></persName><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation></author><author xml:id="author-0016"><persName><forename type="first">M. R. W.</forename><surname>Masheder</surname></persName><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation></author><author xml:id="author-0017"><persName><forename type="first">D. H.</forename><surname>Morgan</surname></persName><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation></author><author xml:id="author-0018"><persName><forename type="first">R. A. H.</forename><surname>Morris</surname></persName><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation></author><author xml:id="author-0019"><persName><forename type="first">D.</forename><surname>Russeil</surname></persName><affiliation>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</affiliation></author><author xml:id="author-0020"><persName><forename type="first">K. S.</forename><surname>Russell</surname></persName><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation></author><author xml:id="author-0021"><persName><forename type="first">R. N. F.</forename><surname>Walker</surname></persName><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation></author><idno type="istex">D6276BED7D62FB067443F2193817ECCDA3997AC7</idno><idno type="ark">ark:/67375/HXZ-DMNVV866-V</idno><idno type="DOI">10.1111/j.1365-2966.2005.09350.x</idno></analytic><monogr><title level="j">Monthly Notices of the Royal Astronomical Society</title><title level="j" type="abbrev">Mon. Not. R. Astron. Soc.</title><idno type="pISSN">0035-8711</idno><idno type="eISSN">1365-2966</idno><idno type="publisher-id">mnras</idno><idno type="PublisherID-hwp">mnras</idno><imprint><publisher>Blackwell Science Ltd</publisher><pubPlace>Oxford, UK</pubPlace><date type="published" when="2005-09-11"></date><biblScope unit="volume">362</biblScope><biblScope unit="issue">2</biblScope><biblScope unit="page" from="689">689</biblScope><biblScope unit="page" to="710">710</biblScope></imprint></monogr></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2005</date></creation><abstract><p>The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N ii] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.</p></abstract><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Key words</head><item><term>astronomical data bases: miscellaneous</term></item><item><term>catalogues</term></item><item><term>surveys</term></item><item><term>stars: emission line</term></item><item><term>photometry</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2005-09-11">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="corpus oup, element #text not found" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0"</istex:xmlDeclaration><istex:docType PUBLIC="-//NLM//DTD Journal Publishing DTD v2.3 20070202//EN" URI="journalpublishing.dtd" name="istex:docType"></istex:docType><istex:document><article article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="hwp">mnras</journal-id>
<journal-id journal-id-type="publisher-id">mnras</journal-id>
<journal-title>Monthly Notices of the Royal Astronomical Society</journal-title>
<abbrev-journal-title>Mon. Not. R. Astron. Soc.</abbrev-journal-title>
<issn pub-type="ppub">0035-8711</issn>
<issn pub-type="epub">1365-2966</issn>
<publisher>
<publisher-name>Blackwell Science Ltd</publisher-name>
<publisher-loc>Oxford, UK</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1111/j.1365-2966.2005.09350.x</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Papers</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>The AAO/UKST SuperCOSMOS Hα survey</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes">
<name><surname>Parker</surname><given-names>Quentin A.</given-names></name><xref ref-type="aff" rid="a1"><sup>1</sup></xref><xref ref-type="aff" rid="a3"><sup>3</sup></xref><xref ref-type="corresp" rid="cor1"><sup>⋆</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Phillipps</surname><given-names>S.</given-names></name><xref ref-type="aff" rid="a2"><sup>2</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Pierce</surname><given-names>M. J.</given-names></name><xref ref-type="aff" rid="a2"><sup>2</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Hartley</surname><given-names>M.</given-names></name><xref ref-type="aff" rid="a4"><sup>4</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Hambly</surname><given-names>N. C.</given-names></name><xref ref-type="aff" rid="a5"><sup>5</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Read</surname><given-names>M. A.</given-names></name><xref ref-type="aff" rid="a5"><sup>5</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>MacGillivray</surname><given-names>H. T.</given-names></name><xref ref-type="aff" rid="a5"><sup>5</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Tritton</surname><given-names>S. B.</given-names></name><xref ref-type="aff" rid="a5"><sup>5</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Cass</surname><given-names>C. P.</given-names></name><xref ref-type="aff" rid="a4"><sup>4</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Cannon</surname><given-names>R. D.</given-names></name><xref ref-type="aff" rid="a3"><sup>3</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Cohen</surname><given-names>M.</given-names></name><xref ref-type="aff" rid="a6"><sup>6</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Drew</surname><given-names>J. E.</given-names></name><xref ref-type="aff" rid="a7"><sup>7</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Frew</surname><given-names>D. J.</given-names></name><xref ref-type="aff" rid="a1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Hopewell</surname><given-names>E.</given-names></name><xref ref-type="aff" rid="a7"><sup>7</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Mader</surname><given-names>S.</given-names></name><xref ref-type="aff" rid="a8"><sup>8</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Malin</surname><given-names>D. F.</given-names></name><xref ref-type="aff" rid="a3"><sup>3</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Masheder</surname><given-names>M. R. W.</given-names></name><xref ref-type="aff" rid="a2"><sup>2</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Morgan</surname><given-names>D. H.</given-names></name><xref ref-type="aff" rid="a5"><sup>5</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Morris</surname><given-names>R. A. H.</given-names></name><xref ref-type="aff" rid="a2"><sup>2</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Russeil</surname><given-names>D.</given-names></name><xref ref-type="aff" rid="a9"><sup>9</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Russell</surname><given-names>K. S.</given-names></name><xref ref-type="aff" rid="a4"><sup>4</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Walker</surname><given-names>R. N. F.</given-names></name><xref ref-type="aff" rid="a2"><sup>2</sup></xref>
</contrib>
<aff id="a1"><label>1</label>Macquarie University, Sydney, Australia</aff>
<aff id="a2"><label>2</label>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</aff>
<aff id="a3"><label>3</label>Anglo-Australian Observatory, Epping, New South Wales, Australia</aff>
<aff id="a4"><label>4</label>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</aff>
<aff id="a5"><label>5</label>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</aff>
<aff id="a6"><label>6</label>UC, Berkeley, USA</aff>
<aff id="a7"><label>7</label>Imperial College, London</aff>
<aff id="a8"><label>8</label>Australia Telescope National Facility, Parkes, Australia</aff>
<aff id="a9"><label>9</label>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</aff>
</contrib-group>
<author-notes>
<corresp id="cor1"><label>⋆</label>E-mail: <email>qap@ics.mq.edu.au</email></corresp>
</author-notes>
<pub-date pub-type="ppub">
<day>11</day>
<month>9</month>
<year>2005</year>
</pub-date>
<volume>362</volume>
<issue>2</issue>
<fpage>689</fpage>
<lpage>710</lpage>
<history>
<date date-type="received">
<day>23</day>
<month>6</month>
<year>2005</year>
</date>
<date date-type="accepted">
<day>23</day>
<month>6</month>
<year>2005</year>
</date>
</history>
<permissions>
<copyright-statement>© 2005 RAS</copyright-statement>
<copyright-year>2005</copyright-year>
</permissions>
<abstract>
<p>The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N <sc>ii</sc>] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of <italic>R</italic>≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.</p>
</abstract>
<kwd-group xml:lang="en">
<title>Key words</title>
<kwd>astronomical data bases: miscellaneous</kwd>
<kwd>catalogues</kwd>
<kwd>surveys</kwd>
<kwd>stars: emission line</kwd>
<kwd>photometry</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec id="ss1" sec-type="intro">
<label>1</label>
<title>Introduction</title>
<p>Hα emission from H <sc>ii</sc> regions is one of the most direct optical tracers of current star formation activity, and is routinely used to measure star formation rates in external galaxies (e.g. <xref ref-type="bibr" rid="bib40">Kennicutt 1992</xref>). In our own Galaxy, H <sc>ii</sc> regions are seen by direct ultraviolet (UV) illumination of molecular clouds from adjacent hot stars and as highly structured shells, bubbles and sheets of emission resulting from supernovae, planetary nebula, Wolf-Rayet stars and other stellar outflows. Some large-scale outflows can, in turn, be themselves a trigger of star formation, and their morphology is strongly influenced by the nature and density of the interstellar medium (ISM) into which they expand. Hα imaging allows this to be studied in great detail in our immediate Galactic neighbourhood and to be detected at a great distance in external galaxies. The UV flux from hot stars also excites a more diffuse emission from the ISM, unconnected to current star formation and detectable over large areas of sky.</p>
<p>The perimeters of some large emission shells appear to enclose the locations of more recent star formation, which may in turn generate further supernovae and stellar winds (<xref ref-type="bibr" rid="bib14">Dopita, Mathewson & Ford 1985</xref>), while their morphology informs the processes by which star formation is propagated (e.g. <xref ref-type="bibr" rid="bib18">Elmegreen & Lada 1977</xref>; <xref ref-type="bibr" rid="bib24">Gerola & Seiden 1978</xref>). Because of proximity, some of these structures can present very large angular sizes such as Barnard's loop (probably the first large-scale emission structure detected in the Galaxy) which subtends 13° (<xref ref-type="bibr" rid="bib64">Pickering 1890</xref>) and the Gum nebula which, at 36°, is even larger (<xref ref-type="bibr" rid="bib26">Gum 1952</xref>). More distant complexes or groups of H <sc>ii</sc> regions, such as NGC 6334, can still be of the order 1° across, and yet present fine detail on arcsecond scales (<xref ref-type="bibr" rid="bib46">Meaburn & White 1982</xref>). Given their interaction with their external large-scale environment (<xref ref-type="bibr" rid="bib80">Tenorio-Tagle & Palous 1987</xref>), it was clear that emission-line imaging of these structures required an efficient wide-field capability and high spatial resolution.</p>
<p>On smaller scales, stellar Hα emission characterizes the short-lived, least well-understood stages of stellar evolution, i.e. those of pre- and post-main sequence stars, planetary nebulae (PNe) and close binary systems. Previous efforts to detect emission sources have either offered modest area coverage; e.g. the UBVI and Hα photometric surveys of <xref ref-type="bibr" rid="bib79">Sung, Chun & Bessell (2000)</xref> or <xref ref-type="bibr" rid="bib39">Keller et al. (2001)</xref> or, where a large-area survey has been conducted, becomes incomplete at relatively bright magnitudes. An example is the objective-prism survey of <xref ref-type="bibr" rid="bib77">Stephenson & Sanduleak (1977)</xref>, which reaches only ∼14 mag. Such surveys are highly incomplete, so their emission source catalogues provide only limited samples upon which to build our understanding of these rarely observed phases of stellar evolution.</p>
<p>From the above, the importance of Galactic Hα line emission from both stars and nebulae is evident, and this has encouraged many surveys for H <sc>ii</sc> regions in particular, e.g. <xref ref-type="bibr" rid="bib74">Sharpless (1953</xref>, <xref ref-type="bibr" rid="bib75">1959</xref>), <xref ref-type="bibr" rid="bib27">Gum (1955)</xref>, <xref ref-type="bibr" rid="bib33">Hase & Shajn (1955)</xref>, <xref ref-type="bibr" rid="bib4">Bok, Bester & Wade (1955)</xref>, <xref ref-type="bibr" rid="bib37">Johnson (1955</xref>, <xref ref-type="bibr" rid="bib38">1956</xref>), <xref ref-type="bibr" rid="bib69">Rodgers, Campbell & Whiteoak (1960)</xref>, <xref ref-type="bibr" rid="bib22">Georgelin & Georgelin (1970)</xref> and <xref ref-type="bibr" rid="bib76">Sivan (1974)</xref>. These earlier surveys were limited to relatively small targeted areas or had such wide fields of view that small-scale detail was lost due to the low angular resolution; e.g. the survey of <xref ref-type="bibr" rid="bib76">Sivan (1974)</xref> used 60° field diameters giving a plate scale of ∼6° mm<sup>−1</sup>. Relatively little optical emission-line survey work had been done in a way that combined wide-angle coverage with good sensitivity and high resolution. These characteristics are essential to allow thorough examination of the morphology and interaction of emission regions with their environment on arcsecond to degree scales and to detect the large variety of stellar emission sources to suitably faint levels.</p>
<p>Hence, in the mid-1990s, a number of the present authors suggested that the UK Schmidt Telescope (UKST) should be used to make a narrow-band photographic Hα survey of the Southern Milky Way and Magellanic Clouds. The only previous wide-area UKST Hα material comes from the work by Meaburn and co-workers in the 1970s (see <xref ref-type="bibr" rid="bib11">Davies, Elliott & Meaburn 1976</xref>; <xref ref-type="bibr" rid="bib45">Meaburn 1980</xref>). They used a 100-Å bandpass multi-element mosaic filter and fast, but coarse grained, 098-04 emulsion. It covered some limited areas close to the Galactic Plane (<xref ref-type="bibr" rid="bib46">Meaburn & White 1982</xref>), but was mainly influential in the study of the ionized gas in the Magellanic Clouds, showing the first evidence for ‘supergiant-shells’ and other large-scale features (<xref ref-type="bibr" rid="bib11">Davies et al. 1976</xref>; <xref ref-type="bibr" rid="bib45">Meaburn 1980</xref>). There are other recent wide-area Hα surveys such as that by the Virginia group in the Northern hemisphere [Virginia Tech Spectratline Survey (VTSS); <xref ref-type="bibr" rid="bib12">Dennison et al. 1998</xref>] and the Mount Stromlo group in the south (<xref ref-type="bibr" rid="bib7">Buxton et al. 1998</xref>). Recently, <xref ref-type="bibr" rid="bib21">Gaustad et al. (2001)</xref> have released the full ‘Southern Hα Sky Survey Atlas’ (SHASSA), covering the entire southern sky. This imaging survey has rather coarse, 48-arcsec pixel and strong artefacts from uncancelled stars in the continuum-subtracted product, but has the major benefit of being directly calibrated in Rayleighs. These surveys continue the tradition of deep, low spatial resolution studies, but use CCDs, which permit low flux densities of a few tenths of a Rayleigh to be achieved.</p>
<p>An alternative approach, taken by the Marseille and Wisconsin Fabry-Perot groups in the southern and northern skies, respectively [see <xref ref-type="bibr" rid="bib70">Russeil et al. 1997</xref>, <xref ref-type="bibr" rid="bib71">1998</xref>; <xref ref-type="bibr" rid="bib28">Haffner et al. 2003</xref> for the Wisconsin Hα Mapper (WHAM)], was to obtain high-resolution spectral (i.e. velocity) data, but again with low spatial resolution (e.g. 1° pixel for WHAM).</p>
<p>A critical comparison between the WHAM, SHASSA and VTSS surveys was undertaken by <xref ref-type="bibr" rid="bib19">Finkbeiner (2003)</xref> who presented a ‘whole-sky’ Hα map. Significantly, none of these major surveys offers the arcsecond spatial resolution of the AAO/UKST Hα survey. A summary of fundamental properties of these modern surveys is given in <xref ref-type="fig" rid="tbl1">Table 1</xref>.</p>
<fig id="tbl1" position="float">
<label>Table 1.</label>
<caption><p>Summary details of various current Hα surveys.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-tbl001.tif"></graphic>
</fig>
</sec>
<sec id="ss2">
<label>2</label>
<title>The AAO/UKST Hα Survey</title>
<p>The AAO/UKST Hα survey provides a 5-Rayleigh sensitivity narrow-band survey of Galactic emission (Hα plus [N <sc>ii</sc>] 6548, 6584 Å) with arcsecond spatial resolution. Henceforth, the survey will be referred to simply as the Hα survey though it is understood that this includes any [N <sc>ii</sc>] emission component that is sampled by the filter bandpass (such emission can completely dominate Hα for some planetary nebula (PN) types for example). Approximately 4000 deg<sup>2</sup> of the Southern Milky Way have been covered to |<italic>b</italic>| ∼ 10–13° together with a separate contiguous region of 700 deg<sup>2</sup> in and around the Magellanic Clouds. Matching 3-h Hα and 15-min broad-band (5900–6900 Å) short red (SR) exposures were taken over the 233 distinct but overlapping fields of the Galactic Plane and 40 fields of the Magellanic Clouds. These were done on 4° centres because of the circular aperture of the Hα interference filter, which has a dielectric coating diameter of about 305 mm (∼5.7°) deposited on a standard 356 × 356 mm red glass (RG610) substrate (refer <xref ref-type="sec" rid="ss5">Section 5</xref>). The overlapping 4° field centres enable full, contiguous coverage in Hα despite the circular filter aperture. Because of the slightly smaller effective field, a new Southern sky-grid of 1111, 4° field centres was created (whose numbers should not be confused with the 893 standard 5° field centres of the UKST Southern Sky Surveys). A map of the survey region in a standard UKST RA/DEC plot together with the new field numbers is available on the SuperCOSMOS Hα Survey (SHS) web site.<xref ref-type="fn" rid="fn1"><sup>1</sup></xref> In the online UKST plate catalogue, these fields have an ‘h’ prefix (e.g. h123) to avoid confusion with the European Southern Observatory/o/Science and Engineering Research Council (ESO/SERC) 5° fields.</p>
<p>The survey began in 1997 and took 6 yr to complete. This latest and final UKST photographic survey was the first large-scale, narrow-band survey undertaken on the telescope, and is the first where the sole method of dissemination to the community is via access to online digital data products. Preliminary survey details and results were given by <xref ref-type="bibr" rid="bib56">Parker & Phillipps (1998</xref>, <xref ref-type="bibr" rid="bib58">2003</xref>). The present paper is intended as the definitive reference for the survey. We describe the key characteristics of the survey, the online data product, some survey limitations, a flux calibration scheme, comparisons with other surveys and a brief overview of the potential for current and future scientific exploitation.</p>
<p>The arcsecond resolution of the AAO/UKST Hα survey makes it a particularly powerful tool, not only for investigating the detailed morphology of emission features across the widest range of angular scales, but also as a means of identifying large numbers of faint point-source Hα emitters, which include cataclysmic variables, T Tauri, Be and symbiotic stars, compact Herbig-Haro objects and unresolved PNe. Given the coincidence of the broad C <sc>iv</sc>/He <sc>ii</sc> blend in late-type Wolf-Rayet stars, these objects can also be detected. Most other comparative surveys (<xref ref-type="fig" rid="tbl1">Table 1</xref>) are largely insensitive to point-source emitters as they lack spatial resolution, being optimized instead for the faintest levels of resolved and diffuse emission.</p>
<p>On larger scales, the detailed spatial structure of the ionized ISM component traced by the new AAO/UKST Hα survey can provide key data for many studies, e.g. mapping of specific areas for detailed spectroscopic follow-up to obtain emission-line gas kinematics or for dynamical studies of star-forming regions, with their implications for the energetics of the central stars. Furthermore, comparisons with other indicators of star formation from other wavebands should provide essential clues to the active mechanisms. The survey also complements the recent Galactic Plane radio maps from Molonglo Observatory Synthesis Telescope (<xref ref-type="bibr" rid="bib25">Green et al. 1999</xref>), the new near-infrared maps from the Two Micron All-Sky Survey (2MASS) (<xref ref-type="bibr" rid="bib36">Jarrett et al. 2000</xref>) and the mid-infrared maps from the <italic>MSX</italic> satellite (<xref ref-type="bibr" rid="bib67">Price et al. 2001</xref>).</p>
<p><xref ref-type="fig" rid="fig1">Fig. 1</xref> presents two panels showing the 233 survey fields (mosaiced together by M. Read) to illustrate the overall survey coverage. The entire survey has been incorporated into an online mosaic within the freeware ‘Zoomify’ environment (see ), which enables preliminary survey visualization and scanning. The lowest resolution map can be zoomed-in to a level where each pixel represents about 12 arcsec. This interactive map is available online.<xref ref-type="fn" rid="fn2"><sup>2</sup></xref> This map is a factor of 18 lower in resolution than the full 0.67 arcsec pixel survey data available online, which should be used for serious scientific work. The success of this survey has led directly to a northern counterpart, currently underway on the 2.5-m Isaac Newton Telescope on La Palma using a wide-field CCD camera and Hα-, <italic>R</italic>- and <italic>I</italic>-band imaging; the Isaac Newton telescope Photometric Hα Survey (IPHAS). This important survey is the subject of a separate paper (<xref ref-type="bibr" rid="bib16">Drew et al. 2005</xref>), though a brief comparison in an overlap region is included later in <xref ref-type="sec" rid="ss12">Section 12</xref>.</p>
<fig id="fig1" position="float">
<label>Figure 1.</label>
<caption><p>All 233 survey fields mosaiced together by M. Read. Top panel covers galactic longitude <italic>l</italic>= 40–310 degrees, bottom panel <italic>l</italic>= 300–210 degrees.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig001.tif"></graphic>
</fig>
</sec>
<sec id="ss3">
<label>3</label>
<title>The Detector: Technical Panchromatic Film-Based Emulsion</title>
<p>The survey was carried out using Kodak Technical Panchromatic (Tech-Pan) Estar based films (e.g. <xref ref-type="bibr" rid="bib41">Kodak 1987</xref>). The superb qualities of this emulsion and its adaptation for UKST use have been described in detail by <xref ref-type="bibr" rid="bib57">Parker & Malin (1999)</xref>, so only a very brief summary is given here. The Tech-Pan emulsion has remarkably high quantum efficiency for a photographic material with hypersensitized films having a Detective Quantum Efficiency approaching 10 per cent (<xref ref-type="bibr" rid="bib63">Phillipps & Parker 1993</xref>). Due to its original development in connection with solar patrol work, it has particularly high efficiency around Hα. The Tech-Pan films are also extremely fine grained, with an inherent resolution of ∼5 μm, leading to an excellent high-resolution imaging capability and a depth for point sources that exceeded that achieved for the more widely used glass-based IIIa-F emulsion by about a magnitude for standard UKST <italic>R</italic>-band survey 1-h exposures (e.g. <xref ref-type="bibr" rid="bib57">Parker & Malin 1999</xref>). These factors, combined with the wide area coverage available to Schmidt photographic surveys, made Tech-Pan an ideal choice for the Southern Galactic Plane Hα survey. The colour term stability of Tech-Pan compared to the IIIa-emulsions used at the UKST is given by <xref ref-type="bibr" rid="bib51">Morgan & Parker (2005)</xref> where these terms are shown to be stable, reproducible, generally small and similar to those previously derived for the older IIIa-emulsions. This gives confidence in the survey's photometric integrity. Over the survey life-time, photography on a Schmidt telescope still offered several advantages over CCD images, especially low cost and very fine spatial resolution and uniformity across a large physical area (356 × 356 mm) giving a 40 deg<sup>2</sup> wide field of view. However, a key limitation is that the detector response is linear over only a narrow dynamic range, so recovering and calibrating the intensity information needs careful treatment (see <xref ref-type="sec" rid="ss11">Section 11</xref>). In <xref ref-type="fig" rid="fig2">Fig. 2</xref>, we present small, 3 × 3 arcmin regions to demonstrate the qualitative difference between the 3-h Hα and 15-min SR Tech-Pan exposures and the standard 60-min <italic>R</italic>-band IIIa-F UKST survey data. This region includes a newly discovered planetary nebula (PHR1706-3544) found from the Hα survey data as part of the Macquarie/AAO/Strasbourg Hα PNe catalogue (<xref ref-type="bibr" rid="bib58">Parker et al. 2003</xref> and in preparation). Note the improved resolution of the Tech-Pan image, the very similar depth of the respective exposures for point sources and the tighter point-spread function (PSF) for the Tech-Pan compared to the IIIa-F emulsion.</p>
<fig id="fig2" position="float">
<label>Figure 2.</label>
<caption><p>3 × 3 arcmin extracts of SuperCOSMOS data around a newly discovered PN (PHR1706-3544) from the 3-h Hα survey data (a — left), matching 15-min Tech-Pan SR data (b — middle) and earlier epoch 60-min IIIa-F <italic>R</italic>-band data (c — right). The new PN is only visible in the Hα image. Note the well-matched depth for point sources between all the three exposures and the improved resolution of the Tech-Pan images compared with the IIIa-F exposure.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig002.tif"></graphic>
</fig>
</sec>
<sec id="ss4">
<label>4</label>
<title>The Narrow-Band Hα Bandpass Filter</title>
<p>To take advantage of the UKST's large field of view, it was necessary to obtain a physically large narrow bandpass filter to be placed as close as possible to the telescope's focal plane. The issues involved with mounting such filters with Schmidt telescopes have been described by <xref ref-type="bibr" rid="bib44">Meaburn (1978)</xref>, and previous large interference filters were generally of the mosaic type (e.g. <xref ref-type="bibr" rid="bib45">Meaburn 1980</xref>). Such smaller scale interference filters are easier to manufacture and can be made of higher optical quality. However, difficulties associated with their mounting often lead to problems of missing data in the filter gaps, degraded, variable resolution and lack of homogeneity over large survey areas, even when the optical quality of the elements themselves is excellent. This was the case for the Meaburn mosaic filters that did not fully deliver the anticipated performance due to an unfortunate index mismatch in optical cement between the components, which resulted in reflection ghosts (which can be got rid of numerically after scanning), coupled with the practical difficulty of mounting the components in a sandwich to eliminate optical path variations (Meaburn, private communication).</p>
<p>Fortunately, it proved possible for the AAO to obtain a custom-made, exceptionally large, monolithic, thin-film interference filter from Barr Associates in the USA, which avoids the problems that can be associated with mosaic filters. Detailed filter specifications and characteristics are given by <xref ref-type="bibr" rid="bib55">Parker & Bland-Hawthorn (1998)</xref>. The essential features are reviewed here for completeness together with some additional modelling of the filter profile in the converging beam when off-axis (see <xref ref-type="bibr" rid="bib65">Pierce 2005</xref> for further details). An RG610 glass substrate was cut to 356 × 356 mm (∼6.5°), the standard size of UKST filters and coated with a multilayer, dielectric stack to give a 3-cavity design with a clear aperture of ∼305-mm diameter and with an effective refractive index of the equivalent monolayer of 1.34. This circular aperture of layered coating constitutes the interference filter so the corners of the square glass substrate do not behave as an Hα filter. Nevertheless, this is probably the world's largest astronomical, narrow-band filter. At the UKST plate scale, this covers an on-sky area roughly 5.7° in diameter (slightly less than the full Schmidt field). To ensure complete and contiguous survey coverage with the circular aperture interference filter, it was necessary to use 4° field centres.</p>
<p>The filter central wavelength was set slightly longward of rest-frame Hα for two reasons, one instrumental and one astronomical. First, the UKST has a fast, <italic>f</italic>/2.48 converging beam. This leads to the interference filter ‘scanning down’ in transmitted wavelengths for off-axis beams compared to beams incident normal to the filter. Secondly, we wished to survey positive velocity gas (in our own and nearby galaxies). Given a bandpass (FWHM) of 70 Å, we chose to centre the filter at 6590 Å in collimated light compared to 6563 Å for rest-frame Hα. The peak filter transmission is around 90 per cent. Measurements of the filter at the Commonwealth Scientific and Industrial Research Organization (CSIRO) National Measurement Laboratory in Sydney quantitatively confirmed the excellent conformity of the filter to our original specifications (see <xref ref-type="bibr" rid="bib55">Parker & Bland-Hawthorn 1998</xref>). First light filter images were obtained in April 1997.</p>
<sec id="ss4-1">
<label>4.1</label>
<title>The filter model</title>
<p><xref ref-type="fig" rid="fig3">Figs 3(a) and (b)</xref> show two spectral scans of the filter, both taken near the centre using light at normal incidence. <xref ref-type="fig" rid="fig3">Fig. 3(a)</xref> is the result of a high-resolution scan around the Hα region and shows that the bandpass is well centred on 6590 Å and has ∼70-Å FWHM. The transmission is high across the reasonably flat top of the bandpass, reaching over 90 per cent. <xref ref-type="fig" rid="fig3">Fig. 3(b)</xref> is based on a scan with an extended spectral range from 4000 to 11 000 Å. The CSIRO tests show that the out-of-band filter transmission is 0.01 per cent or less up to 7600 Å. <xref ref-type="fig" rid="fig3">Fig. 3(b)</xref> shows that the filter does transmit redward of 7600 Å at up to ∼85 per cent, but the survey data will be unaffected by this as the Tech-Pan film used as detector is insensitive beyond 6990 Å.</p>
<fig id="fig3" position="float">
<label>Figure 3.</label>
<caption><p>The upper plot (a) shows a high-resolution transmission scan from central area of the Hα filter. The lower plot (b) shows a wide wavelength range transmission scan from the central area of the Hα filter showing the isolated narrow peak around Hα. Transmission at longer wavelengths is not recorded in the survey data as the Tech-Pan film emulsion cut-off is at 6990 Å and hence not sensitive to light at longer wavelengths.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig003.tif"></graphic>
</fig>
<p>While this satisfies the intended performance of the filter in light of normal incidence, in the <italic>f</italic>/2.48 beam of the UKST, light from an object in the field centre is focused into a cone and enters the filter at a range of angles up to 11.4°. The bandpass of an interference filter is blue-shifted for light entering at an angle. This was modelled by breaking down the contributions from the light cone into a series of concentric rings of size 1° covering the telescope beam over a range 0.4–11.4°, each entering the filter at a different angle. The contribution from the central part of the cone will not be significantly blue-shifted. The spectral shift was calculated for each ring according to <xref ref-type="disp-formula" rid="m1">equation (1)</xref> adapted from <xref ref-type="bibr" rid="bib17">Elliot & Meaburn (1976)</xref>.
<disp-formula id="m1">
<label>(1)</label>
<graphic mimetype="image" xlink:href="362-2-689-eq001.tif"></graphic>
</disp-formula>
</p>
<p>Here λ<sub>0</sub> is the chosen central wavelength for the filter bandpass in this case 6590 Å, λ<sub>θ</sub> is the shifted central wavelength of the filter profile based on the angle, θ, of the incident light and μ is the refractive index. A higher refractive index will minimize the blue shifting of the filter transmission with incident angle of light, and the filter was designed with this in mind. Tests performed by the CSIRO using light at 0, 5 and 10° incidence found the effective refractive index of all the layers combined, i.e. the effective monolayer, is μ= 1.34. This is the value used in <xref ref-type="disp-formula" rid="m1">equation (1)</xref> to generate the shifts for the spectral response of the Hα filter in the UKST beam. These shifts are shown in <xref ref-type="fig" rid="fig4">Fig. 4(a)</xref>. The solid lines are the shifting response curves with the most red response curve being applicable to light of normal incidence and the most blue response curve tracing the filter response to light entering at the most extreme angle from the telescope beam.</p>
<fig id="fig4" position="float">
<label>Figure 4.</label>
<caption><p>Blue-shifting response of interference filter in converging UKST beam as one moves out from the centre of the field. Top plot (a) shows the shift for each concentric ring of the beam; the second plot (b) shows these shifted response curves weighted according to the area of the ring. The final plot (c) shows the summed, smeared out filter transmission curve. The central wavelength of this smeared profile is 6550 Å and the FWHM is 80 Å.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig004.tif"></graphic>
</fig>
<p>In order to combine these to generate a smeared filter response curve, which accounts for the telescope beam, each shifted bandpass is weighted by the area of the contributing ring as a fraction of the whole cone. The weighted response curves are shown in <xref ref-type="fig" rid="fig4">Fig. 4(b)</xref> and the resulting, summed bandpass is shown in <xref ref-type="fig" rid="fig4">Fig. 4(c)</xref>. The FWHM of this smeared bandpass is 80 Å, centred on ∼6550 Å.</p>
<p>This models the transmission of the filter in the centre of a survey field. Towards the edges of the field, the shape of the cone changes and the maximum angle of incidence is over 14°, which will shift the filter response further to the blue. The smeared out filter profile is significant as it permits the calculation of the contribution of the contaminant [N <sc>ii</sc>] lines at 6548 Å and 6584 Å, to the flux recorded by the survey. Based on the smeared out filter response shown in <xref ref-type="fig" rid="fig4">Fig. 4(c)</xref>, the filter transmits H αλ6563 Å at 80 per cent, [N <sc>ii</sc>]λ6548 Å at 82 per cent and [N <sc>ii</sc>]λ6584 Å at 50 per cent. Given that the [N <sc>ii</sc>]λ6584 Å line is quantum mechanically fixed to be three times as strong as the [N <sc>ii</sc>]λ6548 Å line (<xref ref-type="bibr" rid="bib53">Osterbrock 1989</xref>), this gives a transmission of 58 per cent for any [N <sc>ii</sc>] emission compared with 80 per cent transmission for the Hα line. This is especially important when considering PNe because the strength of the [N <sc>ii</sc>] lines varies with respect to the Hα line from PNe to PNe and will have a very significant impact on any calibration scheme based on PNe line flux standards if not taken into account. Of course, for general diffuse Hα emission, the point-to-point Hα-to-[N <sc>ii</sc>] ratio is in general unknown without independent spectroscopic information, so we assume an [N <sc>ii</sc>]/Hα of 0.3, typically used for the warm ionized medium (e.g. <xref ref-type="bibr" rid="bib3">Bland-Hawthorn et al. 1998</xref>).</p>
</sec>
<sec id="ss4-2">
<label>4.2</label>
<title>Survey depth and quality control</title>
<p>The Hα films are not sky-limited after a 3-h exposure, but this was chosen as a pragmatic limit that optimizes depth, image quality and survey productivity. Field rotation and atmospheric differential refraction can adversely affect longer exposures (<xref ref-type="bibr" rid="bib83">Watson 1984</xref>), which are also more susceptible to short-term weather and seeing variations. The associated 15-min broad-band SR exposures were taken through the OG590 red filter. At this exposure level, they are well matched to the depth of continuum point-sources on the matching Hα exposure. For completeness, we include in <xref ref-type="fig" rid="fig5">Fig. 5</xref> the effective SR bandpass as a function of wavelength obtained from a calibration spectrogram for the OG590 filter in combination with the Tech-Pan emulsion.</p>
<fig id="fig5" position="float">
<label>Figure 5.</label>
<caption><p>Calibration spectrograph result of the effective SR bandpass as a function of wavelength from the combination of the red OG590 filter and the Tech-Pan emulsion.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig005.tif"></graphic>
</fig>
<p>With photographic surveys, the magnitude limit for a given survey field is not a fixed parameter but is a function of factors such as seeing, hypersensitization and development of the films after exposure, emulsion batch variations and the brightness of the night-sky. Nevertheless, it is clear from comparison with the generally deeper, standard UKST <italic>R</italic>-band survey data that the approximate magnitude limit for a typical Hα survey field in an equivalent <italic>R</italic> magnitude for continuum point sources is ∼20.5 (<xref ref-type="bibr" rid="bib1">Arrowsmith & Parker 2001</xref>). This value can be directly determined by examining the number magnitude counts from the matched Hα, SR and <italic>R</italic> band SuperCOSMOS Image Analysis Mode (IAM) data (see later) for a given field and determining the point where completeness breaks down. As an illustration, we give magnitude limit estimates for continuum point sources in A and B grade exposures of two Hα survey fields in <xref ref-type="fig" rid="tbl2">Table 2</xref>.</p>
<fig id="tbl2" position="float">
<label>Table 2.</label>
<caption><p>The depth of each of the four original images measured in R equivalent magnitudes.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-tbl002.tif"></graphic>
</fig>
<p>Additionally, the use of the same emulsion for both Hα and SR exposures ensures an excellent correspondence of their image PSFs when film pairs are taken under the same observing conditions. The intention was to take the Hα and SR exposures consecutively as far as possible. This greatly simplifies the inter-comparability of both types of exposure. Of the 233 survey fields, only 100 are in fact sequential pairs while most of the rest were taken a few days apart. However, 45 fields had a gap of one or more years between the Hα and SR survey exposures because one or the other of the exposures had to be repeated to satisfy the stringent survey quality acceptance criteria. Strict quality control has been applied to the survey pairs by M. Hartley and S. Tritton according to well-established criteria before any exposure is allowed to be incorporated into the survey. This ensures that the most uniform and homogeneous data set possible is created. Each exposure grade is determined by means of a score with ‘0’ being the best and ‘3’ being the limit for an exposure to be considered an ‘A’ grade (highest quality). The image grade is recorded in the information and data sheets, which accompany the survey data, together with a letter code to indicate which is the most significant contribution to the score. Long, 3-h exposures are prone to field rotation, which can cause image trailing (denoted by T in the image grade), poor weather can lead to curtailed exposure times (U for underexposed). Cosmetic defects such as emulsion faults (E), haze halos (H) and processing streaks (P) can also contribute to a poor grade. These defects can be present in either the Hα or the SR image. Where possible, any survey exposure that was not rated A grade was repeated. Unfortunately, a few B-grades had to be accepted into the survey, though over 90 per cent were deemed survey quality, maintaining the high standards set for all UKST surveys.</p>
</sec>
</sec>
<sec id="ss5">
<label>5</label>
<title>Astrometric Accuracy of the SHS</title>
<p>Astrometric calibration of survey photographic material measured on SuperCOSMOS is discussed in <xref ref-type="bibr" rid="bib30">Hambly et al. (2001a)</xref>. The calibration procedure consists of applying a six-coefficient (linear) plate model to measured positions of Tycho-2 catalogue reference stars, along with a radial distortion coefficient appropriate to Schmidt optics (i.e. tan <italic>r</italic>/<italic>r</italic>) and a fixed, higher order two-dimensional correction map to account for distortion induced by mechanical deformation of the photographic material when clamped in the telescope plate holder to fit the spherical focal surface. As demonstrated in <xref ref-type="bibr" rid="bib32">Hambly et al. (2001c)</xref>, this yields absolute positional accuracy of typically ±0.2 arcsec for glass plates. The SHS, on the other hand, employs film media, which cannot be as mechanically stable as glass on the largest scales. However, provided a sufficiently dense grid of reference stars is available, it is possible to map out the unique distortion pattern that any one film may present.</p>
<p>In order to achieve the best possible astrometry for the SHS, the generic SuperCOSMOS Sky Survey (SSS) astrometric reduction procedure was modified by replacing the averaged distortion map with a correction stage where the individual film distortion pattern is measured with respect to the U.S. Naval Observatory (USNO) CCD Astrograph Catalogue (UCAC) astrometric reference catalogue (<xref ref-type="bibr" rid="bib84">Zacharias et al. 2004</xref>). In <xref ref-type="fig" rid="fig6">Fig. 6</xref>, we show the results of comparing first-pass SHS astrometry (i.e. without correction of any higher order systematic distortion) with the UCAC catalogue for a single SHS film. Residuals have been averaged in 1-cm boxes and smoothed and filtered using a scale length of 3 box widths. A systematic distortion pattern is clearly seen, and comparing with fig. 1 of <xref ref-type="bibr" rid="bib30">Hambly et al. (2001)</xref> there is no fourfold symmetry in the pattern, which is a characteristic of mechanical deformation of rigid glass plates. Moreover, similar plots for different films show different patterns, so a fixed correction map cannot be applied across the entire survey film set. <xref ref-type="fig" rid="fig7">Figs 7(a) and (b)</xref> show histograms of the residuals of individual UCAC standards from which <xref ref-type="fig" rid="fig6">Fig. 6</xref> is derived; a robustly estimated root mean squared (rms) (i.e. a median of absolute deviations scaled by 1.48, to be equivalent to a Gaussian sigma) is found to be about 0.4 arcsec. Now, if the SHS positional data are corrected during the astrometric reduction procedure using the map values displayed in <xref ref-type="fig" rid="fig6">Fig. 6</xref>, the rms drops to ∼0.3 arcsec; the new histograms of individual residuals are displayed in <xref ref-type="fig" rid="fig7">Figs 7(c) and (d)</xref>. The value of ±0.3 arcsec can be taken as indicative of the typical global astrometric accuracy of the SHS in either co-ordinate, and compares favourably with the figure quoted for the SSS of ∼0.2 arcsec, given the higher level of crowding of the SHS fields.</p>
<fig id="fig6" position="float">
<label>Figure 6.</label>
<caption><p>Systematic astrometric distortion pattern of SHS Hα survey field h67, reduced using a standard six coefficient linear fit plus a radial distortion term, when compared to the UCAC catalogue. The scale size of the vectors is 0.5 arcsec to 1 cm. Systematic positional errors of more than 1 arcsec (corresponding to one tick mark on either axis) are observed in the film data, e.g. in the left-hand corners.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig006.tif"></graphic>
</fig>
<fig id="fig7" position="float">
<label>Figure 7.</label>
<caption><p>Histograms of residuals between SHS and UCAC astrometry (see text) for: (a, b) uncorrected positions and (c, d) positions corrected during the astrometric reduction procedure using the distortion map shown in <xref ref-type="fig" rid="fig6">Fig. 6</xref>. The accuracy is quantified by a robustly estimated rms residual, in either co-ordinate, and shows a ∼30 per cent improvement when the correction map is employed. From this analysis, SHS absolute astrometry is typically accurate to ∼0.3 arcsec.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig007.tif"></graphic>
</fig>
</sec>
<sec id="ss6">
<label>6</label>
<title>The Survey Supercosmos Digital Data</title>
<p>The high-speed ‘SuperCOSMOS’ measuring machine at the Royal Observatory Edinburgh (e.g. <xref ref-type="bibr" rid="bib48">Miller et al. 1992</xref>; <xref ref-type="bibr" rid="bib29">Hambly et al. 1998</xref>) has been used to scan the Hα and SR exposure A-grade pairs at 10-μm (0.67 arcsec) resolution. The same general scanning and post-processing reduction process is employed as for the directly analogous SuperCOSMOS broad-band surveys of the Southern Sky (SSS) currently online and outlined in detail by <xref ref-type="bibr" rid="bib30">Hambly et al. (2001a)</xref>; <xref ref-type="bibr" rid="bib31">Hambly, Irwin & MacGillivray (2001b)</xref>; <xref ref-type="bibr" rid="bib32">Hambly et al. (2001c)</xref>. The user interface is broadly equivalent, and the main features are summarized neatly in fig. 1 of <xref ref-type="bibr" rid="bib30">Hambly et al. (2001a)</xref>. However, due to the special nature of the survey, some additional processing steps and Hα specific options have been added to create the online SHS described below.</p>
<sec id="ss6-1">
<label>6.1</label>
<title>Basic characteristics of the online ‘SHS’ Hα survey</title>
<p>The Wide-Field Astronomy Unit (WFAU) of the Institute for Astronomy Edinburgh is responsible for maintaining the Hα survey data products. Both the Hα and SR data for the 233 Southern Galactic Plane survey fields are available online.<xref ref-type="fn" rid="fn3"><sup>3</sup></xref> Unfortunately, there are no plans for the 40-field Magellanic Cloud Hα and SR survey pairs to also be put online. The data products are given as Flexible Image Transport System (FITS) files (see ) with comprehensive FITS header information detailing key photographic, photometric, astrometric and scanning parameters (e.g. <xref ref-type="bibr" rid="bib31">Hambly et al. 2001b</xref>). The FITS images also have an accurate built-in World Co-ordinate System (WCS). This permits easy incorporation into other software packages such as the <sc>starlink</sc><italic>GAIA</italic> environment for subsequent visualization, investigation, manipulation and comparison with other data. The entire survey data are stored on a random array of independent disks for fast access, and a comprehensive set of web-based documentation has been provided. The pixel data map for each field is about 2 Gb. The scanned pixel data are processed through the standard SuperCOSMOS thresholded object detection and parametrization software (e.g. <xref ref-type="bibr" rid="bib2">Beard, MacGillivray & Thanisch 1990</xref>) to produce the associated IAM data for each field. This process determines a set of 32 image-moment parameters, which provide the astrometry, photometry and morphology of the detected objects. Full details of the image detection and parametrization are given in <xref ref-type="bibr" rid="bib31">Hambly et al. (2001b)</xref>. For the SHS survey, a selection of the 32 most important IAM parameters from the merging of the Hα, SR and <italic>I</italic>-band data for each detected image in the SHS are available and are given in <xref ref-type="fig" rid="tbl3">Table 3</xref>.</p>
<fig id="tbl3" position="float">
<label>Table 3.</label>
<caption><p>The selected 32 IAM parameters used in the merged SHS catalogue data</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-tbl003.tif"></graphic>
</fig>
<p>The full resolution, 10-μm pixel data and associated IAM parametrized data for both the Hα and SR scanned exposures are stored online on a field by field basis. On the SuperCOSMOS web site, the scanned survey data for each field has the prefix ‘HAL’ before the survey field number (so Hα survey field h350 = HAL0350, for example, when referring to the online digital SuperCOSMOS data). The SR images have been transformed to exactly match the pixel grid of the master Hα exposures, which permits direct image blinking and comparison between the pixel data for each field. The general Hα survey data products are accessed via a web interface that has the same look and feel as the existing broad-band SuperCOSMOS online ‘SSS’ surveys but with some additional functionality. The IAM data produced for each field can be downloaded separately if desired or assembled into seamless catalogues on-the-fly, which can cover several adjacent fields using the ‘Get a Catalogue’ option. The combined IAM data are organized into a full listing of 53 image parameters or a more manageable subset of the most useful 32 as in <xref ref-type="fig" rid="tbl3">Table 3</xref>. A set of ‘expert’ options is also available to further select catalogue extraction parameters. A special feature to create a difference image of each field following variable image PSF matching techniques developed by <xref ref-type="bibr" rid="bib5">Bond et al. (2001)</xref> also exists to permit large-scale resolved emission maps to be created with reduced artefacts from uncancelled stars. This can be computationally intensive, and so is not generally available without prior arrangement with the WFAU. For most applications, simple quotient imaging between the Hα and SR pixel data is sufficient due to the well-matched PSFs and depth.</p>
<p>A 16× blocked-down version of each field is also available as both a GIF image and as an FITS file, which has the WCS built in to the FITS header. These whole field maps can be studied to select smaller regions of interest for extraction at full resolution using the ‘Get an Image’ option. The full resolution pixel data access limit is currently set at 9000 arcmin<sup>2</sup> with regions downloaded as FITS files (also with WCS) and both the SR and the Hα data for the same region can be downloaded simultaneously. Areas for extraction can be chosen via equatorial (J2000 or B1950) or Galactic <italic>(l,b)</italic> co-ordinates in a variable <italic>m</italic>×<italic>n</italic> arcmin rectangular region format. A clickable map of the current fields online enables individual field details to be displayed prior to viewing the blocked full field image. A batch mode enables large numbers of thumb-nail images to be extracted around objects of interest with the option to return Hα and/or SR postscript plots of the extracted images. An option to apply a ‘Flat-Field’ to the Hα pixel data in intensity space is included to permit correction of the non-uniformities in the measured exposures arising from the excellent but slightly varying Hα filter transmission profile. This has been shown to work effectively and is described in <xref ref-type="sec" rid="ss9">Section 9</xref>. A radius of 153 mm (∼2.85 degrees) from each survey field centre has been adopted as the region with good data (<15 per cent correction factors). The ‘good data’ radius from each scanned Hα field centre has been used in creating a confidence map, which is incorporated into the extracted FITS image as an additional FITS extension (extension [3], e.g. test-image.fits[3]). This can be used to flag areas of the extracted image that might not be quite as good as others. Currently, this has values of 100 for regions extracted interior to this radius and 0 for regions outside.</p>
</sec>
<sec id="ss6-2">
<label>6.2</label>
<title>Incorporation of the SSS ‘<italic>I</italic>’-band data</title>
<p>The IAM catalogue downloaded directly via the ‘Get a Catalogue’ option or as incorporated in the FITS table extension to the downloaded pixel data via the ‘Get an Image’ option contains information not just from the Hα and the SR images, but also from the SERC-I (near infrared) survey, which has been carefully matched with the SHS data. The <italic>I</italic>-band data are particularly useful when searching for point-source Hα emitters, as it can help to eliminate contamination from late-type stars. However, there are issues that any user should be aware of when combining the <italic>I</italic>-band data with the SHS magnitudes. When calibrating UKST data, positional and magnitude-dependent systematic errors are present as a result of variations in emulsion sensitivity and vignetting towards the image corners (<xref ref-type="bibr" rid="bib31">Hambly et al. 2001b</xref>). The <italic>I</italic>-band survey was taken on standard ESO/SERC 5° field centres, so the vignetting will have a different effect on the two sets of photometry at a given survey location. Furthermore, the <italic>I</italic>-band data are calibrated to relatively few standards. These differences are evident when looking at a plot of SR magnitude versus <italic>R</italic>-<italic>I</italic> colour derived from the SR and paired <italic>I</italic>-band photometry. <xref ref-type="fig" rid="fig8">Fig. 8</xref> shows two colour-magnitude diagrams (CMD) for stars taken from a 10-arcmin region centred on the middle of SHS field h1109 in Monoceros where the low Galactic reddening of <italic>E</italic>(<italic>B</italic>−<italic>V</italic>) = 0.24 (<xref ref-type="bibr" rid="bib73">Schlegel, Finkbeiner & Davis 1998</xref>) should leave the <italic>R</italic>-<italic>I</italic> colour roughly constant for much of the observed magnitude range. <xref ref-type="fig" rid="fig8">Fig. 8(a)</xref> shows the raw result, where a large, unphysical variation of 3.5 mag is seen in the <italic>R</italic>-<italic>I</italic> colour from the brightest to the faintest objects. This is removed as a first-order correction from the survey data by selecting a master colour, in this case the SR, and correcting the <italic>I</italic>-band across all survey fields. Note, however, that at fainter limits one in fact expects redder <italic>R</italic>-<italic>I</italic> colours as such stars are likely to be further away and prone to be more dust reddened or intrinsically fainter and therefore more likely to be late types. Hence, some modest slope is expected. <xref ref-type="fig" rid="fig8">Fig. 8(b)</xref> shows the CMD for the same patch of sky after the colour correction is applied, giving a result in better agreement with expectation. The data can be downloaded in corrected or uncorrected form via an option in the ‘Expert’ parameters of the SHS web site. It is important to ensure that the <italic>I</italic>-band correction is not applied inappropriately, i.e. in a field of intrinsically high reddening, as such a correction will remove genuine features from the data. It should be used with caution.</p>
<fig id="fig8" position="float">
<label>Figure 8.</label>
<caption><p>Plots of SR magnitude versus <italic>R</italic>−<italic>I</italic>, from a 10-arcmin square region in Monoceros, before colour correction for positional and magnitude dependent errors (a — upper) and after (b — lower).</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig008.tif"></graphic>
</fig>
</sec>
</sec>
<sec id="ss7">
<label>7</label>
<title>SHS Point Source Photometry</title>
<p>A significant advantage of the SHS data over its rivals is the ability to detect point sources that have been photometrically calibrated to CCD standards (e.g. <xref ref-type="bibr" rid="bib6">Boyle, Shanks & Croom 1995</xref>; <xref ref-type="bibr" rid="bib10">Croom et al. 1999</xref>). With measurements of isophotal magnitude and object classifications, it is possible to apply a photometric calibration to the Hα and SR films by comparing the SuperCOSMOS raw magnitudes of stars from the Tycho-2 Catalogue (<xref ref-type="bibr" rid="bib34">Hog et al. 2000</xref>) and the Guide Star Photometric Catalogue (<xref ref-type="bibr" rid="bib42">Lasker et al. 1988</xref>). These in turn are checked against photometric standards derived from the CCD observations given by <xref ref-type="bibr" rid="bib10">Croom et al. (1999)</xref> and <xref ref-type="bibr" rid="bib6">Boyle et al. (1995)</xref>. The narrow-band Hα images are calibrated to an ‘R-equivalent’ scale. The 3-h Hα and 15-min SR exposures are matched so that both reach similar depths of R ≃ 20.5 for point sources. Where an object is detected in one band but not in the other, a default value of 99.999 is given in the catalogue data for the magnitude in the missing bandpass. Positional and magnitude-dependent errors are seen in the raw photometric data, created by varying transmission profile and diffraction effects through the thick (5.5 mm) Hα filter, but these are corrected for in the data available through the SHS web site by comparison with the SR data. Photometric consistency is achieved by using the overlap regions between fields to match zero-points across the survey. These corrected magnitudes provide a means of selecting point-source emitters. The variations in measured IAM stellar parameters as a function of field position arising from the variable PSF from field rotation, vignetting, etc., especially at large radii from the field centres, requires that such selection is performed over limited 1-degree areas. In this way, stars with an emission line at Hα will show an enhanced Hα magnitude compared with the SR magnitude. At the bright end of the magnitude distribution, severe photographic and SuperCOSMOS saturation effects come in to play, limiting stellar photometry to R of about 11–12 in both the Hα and SR pass-bands.</p>
</sec>
<sec id="ss8">
<label>8</label>
<title>Spurious Images in the SHS</title>
<p>Spurious images appear from time to time in all photographic images scanned by SuperCOSMOS. They have a variety of forms and causes, and are present in images extracted from the SSS as well as SHS. They can sometimes be picked up by examination of the pixel images directly, though they are often missed, and can also appear as spurious detections in the IAM data. They have a variety of sizes and shapes and may be in or out of focus depending on whether the contaminating source is on the emulsion surface or on the platen used by SuperCOSMOS to sandwich the film flat for scanning. Here, we differentiate between spurious images in the emulsion itself caused by processing defects, emulsion flaws and static marks, and those caused by foreign objects on the surface of the emulsion or on the back of the film. Holes and scratches in the emulsion surface can also give rise to spurious images. Satellite trails and transient phenomenon also give rise to real developed images, which may have no counterpart in other survey bands of the same region. We do not consider these here.</p>
<sec id="ss8-1">
<label>8.1</label>
<title>Basic causes</title>
<p>The SuperCOSMOS facility is situated in a class-100 clean room, and each film is pressure air-cleaned prior to scanning. However, despite best efforts, particles that may already have been present on the emulsion before shipment to SuperCOSMOS manifest themselves as spurious images. The biggest cause is fine particulate dust (20–100 μm). Unfortunately, the Estar film base of the Tech-Pan emulsion is prone to static charge build-up.</p>
</sec>
<sec id="ss8-2">
<label>8.2</label>
<title>Recognizing spurious images</title>
<p>The SuperCOSMOS scanning system is highly specular, so detritus present on the emulsion surface that is often invisible when viewed under diffuse illumination conditions (such as on a light table) is revealed in sharp relief in the SuperCOSMOS data. The number of artefacts seen in the SHS data is somewhat worse than on other glass plate-based surveys of the SSS. Fortunately, having matched exposures in two bands makes the identification of such artefacts more straightforward. For example, since the Hα and SR exposures are registered on the same pixel grid, quotient imaging can reveal the locations of spurious images. A 5 × 5 arcmin region extracted from h273, a field with a particularly high number of spurious images, is shown in <xref ref-type="fig" rid="fig9">Fig. 9</xref>.</p>
<fig id="fig9" position="float">
<label>Figure 9.</label>
<caption><p>5 × 5 arcmin extracts of SuperCOSMOS Hα data from SHS survey field h273 highlighting contaminating spurious images together with a matching image with the IAM data overlaid and with all the spurious images in the frame highlighted.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig009.tif"></graphic>
</fig>
<p>We can take advantage of the fact that the pixel image properties of spurious images are usually quite distinct from real astronomical images, often having a sharpness below that possible from the combination of telescope optics and seeing disc. Their shapes are often highly irregular and non-symmetrical such that they would not fit any normal PSF. This makes them amenable to Fourier filtering. Objects that have no counterpart in the other band are potential spurious image candidates though variable objects, novae and the effects of de-blending complicate the issue significantly. Various IAM parameters, such as the profile statistic, ellipticity, etc., may also aid in identification. Furthermore, spurious IAM objects arising from de-blending overlaying contaminating fibres or hairs usually have very high ellipticities, which may help in isolating likely candidates. <xref ref-type="bibr" rid="bib78">Storkey et al. (2004)</xref> discuss techniques for recognizing and eliminating spurious objects in the online SuperCOSMOS surveys. As yet, this procedure has not been applied to the SHS data.</p>
</sec>
</sec>
<sec id="ss9">
<label>9</label>
<title>Flat-Fielding of the Survey Data</title>
<p>For any interference filter of the size used here, low-level non-uniformities exist, which lead to residual non-physical background variations in the exposed images. In order to establish the magnitude of such effects, three flat-field exposures were taken with the filter subject to uniform illumination. The flat-field images permitted the evaluation of the combined effects of filter transmission in the fast, <italic>f</italic>/2.48 Schmidt beam and telescope vignetting (see UKST Unit handbook, <xref ref-type="bibr" rid="bib81">Tritton 1983</xref>). The flat-field images were exposed to place them on the linear portion of the film's characteristic curve, and were averaged to give the filter/telescope transmission profile shown in <xref ref-type="fig" rid="fig10">Figs 10(a) and (b)</xref>.</p>
<fig id="fig10" position="float">
<label>Figure 10.</label>
<caption><p>(a — top) Contour plot of the narrow-band Hα filter transmission over the SuperCOSMOS scanned area of 5.156° (1728 × 1728 pixel). The contours are plotted at 85, 90, 92, 95, 97 and 98 per cent. The bottom image (b) is a histogram equalization of the same flat-field data, which reveals the filter artefacts present at the 0.1 per cent level.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig010.tif"></graphic>
</fig>
<p><xref ref-type="fig" rid="fig10">Fig. 10(a)</xref> shows transmission contours at 85, 90, 92, 95, 97 and 98 per cent of maximum transmission in the central region. The response is seen to be asymmetric, with the 97 per cent contour extending beyond the edge of the 5.16° field on the right, which corresponds to the west of the survey fields. In the east, the transmission decreases more rapidly, reaching 85 per cent at the eastern edge. Towards the filter corners the transmission drops further. However, the 4° overlapping centres (<xref ref-type="sec" rid="ss4">Section 4</xref>) and the asymmetric nature of the response allows the selection of Hα data requiring flat-field correction of less than 15 per cent for any given area of sky, provided that adjacent fields are available. Most data will require much smaller flat-field corrections. The effect of flat-field corrections as large as 15 per cent on pixel data is considered in the survey calibration section. <xref ref-type="fig" rid="fig10">Fig. 10(b)</xref> is a histogram equalization of the actual flat-field pixel map that reveals the extremely low level artefacts present at the 0.1 per cent level, which are invisible in a linear rendition. The flat-field correction has been stored as a transmission array with maximum value unity, so it is applied by dividing survey image values in intensity space by the relevant correction array elements. This is available as the default option on the SHS web site. The correction breaks down towards the corners of the scanned image and in regions outside of the clear aperture because the density of the exposures at the edges of the circular aperture is too low to lie on the straight line portion of the characteristic curve leading to an overcorrection and also because the Hα filter transmission is becoming increasingly skewed in these extreme regions. Raw transmission or photographic density values and generically calibrated intensity values without flat-field correction can also be requested on the download form. The IAM data are obtained from the raw SuperCOSMOS scans without flat-field correction.</p>
<sec id="ss9-1">
<label>9.1</label>
<title>Specific filter features</title>
<p>Despite the superb quality of the filter, low-level, large-scale variations in transmitted flux can be seen in the Hα survey images under certain exposure conditions. In particular, there are two parallel bands of slightly enhanced transmission (leading to elevated photographic density) going E-W in the north and south of the filter. These bands are only 1–3 per cent higher in intensity than the surrounding regions. A series of low-level artefacts, which are not obvious in the contour plot because they are at a level of <1 per cent, can just be discerned in the filter transmission image in <xref ref-type="fig" rid="fig10">Figs 10(a) and (b)</xref>. They can also just be seen in the contour plot as the spike in the 98 per cent contour just right of centre. The observed shape of these artefacts mimics the series of shallow concentric grooves scored into the surface of the mandrel to enable the Tech-Pan film to be sucked under light vacuum to the curved focal surface of the plate-holder to ensure proper focus. They are thought to arise from the backscattering off these grooves of light that has passed right through the film. Again, it is gratifying that these artefacts, present at the <0.1 per cent level, are effectively removed by application of the flat-field.</p>
</sec>
<sec id="ss9-2">
<label>9.2</label>
<title>Application of the flat-field and correction validity</title>
<p>Field h410, which sits away from the Galactic Plane on the extreme edge of the survey at (<italic>l</italic>, <italic>b</italic>) 330.2°, + 10.28°, has been chosen to test the validity of the flat-field correction as it contains a very low-level isotropic background of Galactic line emission. In the survey image, this will be moderated by the filter response. <xref ref-type="fig" rid="fig11">Figs 11(a) and (b)</xref> show two 16× blocked down images of survey field h410. The top image (<xref ref-type="fig" rid="fig11">Fig. 11a</xref>) is the raw Hα data before the application of the flat-field correction. The structure evident on the field as lighter areas is not Galactic emission but matches the filter transmission profile. The two horizontal bars are present, and the image is less exposed towards the corners where the recorded intensity is lower and the star density also falls. The bright star just to the right of centre is ε Lupi.</p>
<fig id="fig11" position="float">
<label>Figure 11.</label>
<caption><p>Two 16× blocked down, 5.156° SHS Hα images of field h410. The top image (a) is the raw intensity data without flat field correction. The bright areas trace not Galactic emission but the filter transmission profile seen in <xref ref-type="fig" rid="fig10">Fig. 10</xref>. The bottom image (b) has had the flat-field correction applied, which successfully removes the filter artefacts from within the circular aperture.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig011.tif"></graphic>
</fig>
<p>Application of the flat-field correction results in <xref ref-type="fig" rid="fig11">Fig. 11(b)</xref>, which should have a flat background wash of emission across it. The structure from the filter is no longer evident and the bright areas are now in the corners, where the larger flat-field correction over-corrects the SuperCOSMOS intensity counts. This will not adversely affect the majority of the pixel data available on the SHS web site. Data can always be taken from the best area of filter response and no flat-field correction larger than 15 per cent is necessary for any of the survey data that overlap a neighbouring field. Data from the edge of the survey, where no adjacent field exists, have been made available and may require a correction greater than 15 per cent. Areas affected in this way are flagged in the third extension table, which accompanies the downloaded FITS image.</p>
</sec>
</sec>
<sec id="ss10">
<label>10</label>
<title>Geocoronal Hα Emission</title>
<p>Geocoronal Hα emission is caused by fluorescence after solar Lyman β excitation of atomic hydrogen in the exosphere. Because imaging surveys lack velocity resolution for the emission they record, the geocoronal contribution will be present in all of them but indistinguishable from bona fide Galactic Hα emission. Fortunately, one modern Hα survey, WHAM (e.g. <xref ref-type="bibr" rid="bib28">Haffner et al. 2003</xref>), offers very good velocity resolution (∼12 km s<sup>−1</sup>) and is able to separate the atmospheric emission from the Galactic emission and measure the intensity. <xref ref-type="bibr" rid="bib52">Nossal et al. (2001)</xref> report on Hα observations carried out by the WHAM instrument in 1997, the same time as the SHS imaging was starting at the UKST. They find that the geocoronal emission intensity depends on how much the Earth shades the line of sight from sunlight. Their resulting plot of geocoronal Hα emission as a function of Earth shadow height shows that at heights greater than 6000 km only a very low level ∼2 R wash of geocoronal Hα emission is present. Based on the observational information available in the headers of the SHS images, it is possible to calculate the shadow heights for any field. For a random sample of six SHS fields, the shadow height for the whole 3-h observation and across the five-degree field of view was found to be greater than 6000 km, so low-level geocoronal emission is not problematic, as most Galactic Plane fields covered by the SHS will contain significantly stronger emission.</p>
</sec>
<sec id="ss11">
<label>11</label>
<title>Application of an Absolute Calibration to the Hα Survey Data</title>
<p>The AAO/UKST Hα survey data need an absolute intensity calibration if the full scientific value of its sensitivity to faint, diffuse emission is to be realized. The intensity calibration must provide a reliable means of transforming the pixel intensity values from SuperCOSMOS scans of the Hα images into meaningful intensity units such as Rayleighs, which is consistent from field to field. We show that continuum emission can be successfully removed from the Hα images by scaling and subtracting the SR continuum image. Unlike CCD data, which enjoy a linear response over a wide range of emission strength, photographic data can be very difficult to calibrate because the response of the emulsion and SuperCOSMOS scanner is linear only over a relatively small dynamic range. Variations in sensitivity and background occur from exposure to exposure, especially when the Hα and SR pairs were taken on different nights, phases of the moon, etc. Despite this, we show that the survey data have been well exposed to capture Galactic emission on the linear part of the characteristic curve and can be calibrated by means of comparison with the complementary, accurately intensity calibrated SHASSA survey (<xref ref-type="bibr" rid="bib21">Gaustad et al. 2001</xref>). This process does not form part of the current SHS release, but can be undertaken by the user as required.</p>
<sec id="ss11-1">
<label>11.1</label>
<title>Image comparison with SHASSA</title>
<p>The Southern Hα Sky Survey Atlas by <xref ref-type="bibr" rid="bib21">Gaustad et al. (2001)</xref> provides wide-field narrow-band CCD Hα images of the southern sky below Δ =+15° taken with a robotic imaging camera sited at Cerro Tololo Inter-American Observatory (CTIO). The camera used a small, fast, <italic>f</italic>/1.6 Canon lens, which gave a very large (13°) field of view and a spatial resolution of 48 arcsec. Each SHASSA field was imaged through a narrow-band interference filter of width 32 Å centred at 6563 Å as well as a continuum filter with two bands of 61 Å at 6440 Å and 6770 Å on either side the Hα line. The SHASSA web site<xref ref-type="fn" rid="fn4"><sup>4</sup></xref> makes available the raw Hα and continuum images as well as 48 arcsec and 4 arcmin resolution continuum subtracted, intensity calibrated data. The SHS data are superior in terms of resolution while the general sensitivity of both surveys appears qualitatively similar for large-scale emission features. For example, in <xref ref-type="fig" rid="fig12">Fig. 12</xref> we present SHS and SHASSA images of the H <sc>ii</sc> region RCW 19.</p>
<fig id="fig12" position="float">
<label>Figure 12.</label>
<caption><p>An 105 × 75-arcmin region centred on well-known H <sc>ii</sc> region RCW 19 (GUM 10) at α, Δ = 08<sup>h</sup>16<sup>m</sup>17<sup>s</sup>, −35°57′58″ (J2000) extracted from the SHS survey (top left) and the equivalent SHASSA region (top right). A full resolution 8.3 × 4.6 arcmin region from the SHS survey data is shown below centred on the southern H <sc>ii</sc> region component at 08<sup>h</sup>19<sup>m</sup>, −36°14' and indicated in the lower resolution SHS image with a rectangle.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig012.tif"></graphic>
</fig>
</sec>
<sec id="ss11-2">
<label>11.2</label>
<title>The SHASSA intensity calibration</title>
<p>The SHASSA intensity calibration was derived from the planetary nebula spectrophotometric standards of <xref ref-type="bibr" rid="bib13">Dopita & Hua (1997)</xref> after the continuum images had been scaled and subtracted from the Hα frames. Aperture photometry for eighteen of the bright PNe standards was measured from the SHASSA images and used to calculate the calibration factor for the whole survey. A difficulty in applying PNe line fluxes to Hα narrow-band imaging is the proximity of the two [N <sc>ii</sc>]λλ6548, 6584 Å lines, which are included in the flanks of the SHASSA Hα filter bandpass. These vary in strength relative to Hα between PNe and could significantly affect the result. Calculating the transmission properties of the interference filter to these lines is complicated by the blue-shifting of the bandpass with incident angle, an effect that must be treated carefully in the SHS data as the filter sits in the fast <italic>f</italic>/2.48 beam of the UKST. This problem is not as severe for the SHASSA data because in this case the filter sits in front of the camera lens, leaving only the effects of the very large field of view. These effects are considered in <xref ref-type="sec" rid="ss4">section 4</xref> of <xref ref-type="bibr" rid="bib21">Gaustad et al. (2001)</xref> and carefully accounted for in their calibration.</p>
<p>To allow a more detailed comparison, aperture photometry for 87 PNe with a range of surface brightness and integrated flux and with an independent measure of Hα flux was carried out on SHASSA images. Published spectroscopic data were used to deconvolve the contribution from the [N <sc>ii</sc>] lines passed by the SHASSA filter. The results agree with published data to Δ F (H α) =−0.01 dex, σ= 0.05 for SHASSA minus literature fluxes (<xref ref-type="bibr" rid="bib20">Frew 2005</xref>, in preparation; cf. <xref ref-type="bibr" rid="bib66">Pierce et al. 2004</xref>). Since the PNe literature fluxes have associated errors, the SHASSA calibration is better than ±10 per cent across the whole survey, in agreement with the nominal error supplied by <xref ref-type="bibr" rid="bib21">Gaustad et al. (2001)</xref>.</p>
<p>An additional uncertainty is introduced to the zero-point of the SHASSA intensity calibration from the contribution of geocoronal emission. <xref ref-type="bibr" rid="bib21">Gaustad et al. (2001)</xref> estimate this by comparison with overlapping WHAM data points and interpolating where there are none. Our check of the intensity calibration against independent flux measures of PNe indicates that the geocoronal contribution to the SHASSA Hα images has been successfully removed. <xref ref-type="bibr" rid="bib19">Finkbeiner (2003)</xref> also showed there is no significant offset between WHAM and SHASSA data. So we conclude that the SHASSA data has been well calibrated to a zero-point consistent with independent measurements and therefore have confidence in its use as a baseline calibration for the SHS data.</p>
</sec>
<sec id="ss11-3">
<label>11.3</label>
<title>Continuum Subtraction of the SHS</title>
<p>Diffuse emission recorded through the narrow-band Hα filter on the Tech-Pan films will be a combination of Galactic Hα line emission, continuum emission, night-sky auroral lines and geocoronal emission. Ideally, all of these components would need to be disentangled to extract just the Galactic Hα emission. In practice, the geocoronal and auroral emission is considered as a low (∼2 R) level but temporally varying uniform wash, which simply elevates the general background on each exposure to a slightly varying degree.</p>
<p>The matching SR images provide a measure of the continuum component and, properly scaled, can be used to produce continuum subtracted Hα images. Although the Hα and SR exposures are generally exposed to attain the same depth for continuum point sources, the nature of photography and the vagaries of the observing conditions (e.g. if the exposure pairs were not contemporaneous and taken in different moon phases or if the seeing changed) mean that the depth and image quality between the Hα and SR exposures can and does vary. Hence, it is necessary to determine a continuum subtraction scaling factor between Hα and SR on a field-by-field basis. This factor must be precisely determined for the continuum subtraction to be effective. For high-dynamic range CCD exposures, the standard method for determining the appropriate scaling factor to subtract continuum from narrow-band is to compare aperture photometry for stars on both images whose exposures are normally interleaved on short time-scales.</p>
<p>Unfortunately, this does not work well with the Hα SR film exposure pairs (<xref ref-type="bibr" rid="bib65">Pierce 2005</xref>), often leading to under or oversubtraction of the continuum. This arises due to varying backgrounds on the film exposures caused by low-level emulsion sensitivity variations between films (especially if they come from different hypersensitized batches), inherent chemical fog variations in the emulsion, processing variations and true sky background variations arising for the reasons given above. These varying backgrounds result in the same magnitude stars saturating at different levels on different exposures as their Gaussian point spread functions are superimposed on top of any diffuse emission and elevated background, which can severely truncate their peaks. The limited dynamic range of SuperCOSMOS also acts as a further low ceiling above the background, which leaves little room for these bright stellar Gaussians making it hard to effectively utilize stellar photometry to determine the correct scaling factors.</p>
<p>Fortunately, we are able to use the existing SHASSA data to provide a well-determined scale with an independently confirmed zero-point to compare with and calibrate the SHS images. Even exposure pairs taken years apart can be successfully continuum subtracted. A detailed investigation of the SHS calibration process has been undertaken by <xref ref-type="bibr" rid="bib65">Pierce (2005)</xref> but the essential aspects of this process and its application are given here. For example, <xref ref-type="fig" rid="fig13">Fig. 13</xref> shows three images of a 30-arcmin region taken from field h350, which shows strong, varying Galactic Hα emission. The top image is the Hα image downloaded from the SHS web site, the middle image is its SR counterpart, while the bottom image has had the SR ‘continuum’ image scaled and subtracted via a comparison with SHASSA data. In general, this subtraction is very good, removing most of the stellar images and the diffuse continuum. Only the stars that sit in the strongest emission have been oversubtracted and appear as white spots in the image.</p>
<fig id="fig13" position="float">
<label>Figure 13.</label>
<caption><p>Thirty arcminute region at 16<sup>h</sup>47<sup>m</sup>, −49°00' (J2000) from near the centre of SHS field h350 with bright areas of emission shown darkest. The top image is the raw Hα image, the middle the matching SR, while the bottom image is a continuum-subtracted image of the same area. The subtraction, based on a comparison with SHASSA data, has worked well, leaving only minor residuals around stars on the bright diffuse emission.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig013.tif"></graphic>
</fig>
<p>For a given area of sky, pixel data from each survey can be downloaded and, after matching for spatial resolution, the SuperCOSMOS intensity counts can be compared directly with the Rayleigh values in the SHASSA data. A plot of continuum-subtracted SHASSA pixels against equivalent SHS pixels should return a linear relation with a common zero point if the reduction and intensity calibration have been properly carried out. Comparing incorrectly continuum-subtracted SHS data with SHASSA data results in an offset between the two surveys. A range of values for the scaling factor can be applied to the SHS data until the zero-point of the continuum-subtracted UKST survey images best match the zero-point of the equivalent SHASSA data, indicating the appropriate value to use. A calibration based on the SHASSA data will provide an advantage for the SHS over the CTIO survey as it can be applied to the full resolution pixel data. This offers the chance to determine intensities for emission structures not resolved by SHASSA such as the new sample of extended PNe discovered from the SHS data (e.g. Parker et al. 2003b, 2005, <xref ref-type="bibr" rid="bib66">Pierce et al. 2004</xref>, Frew & Parker, in preparation and see <xref ref-type="sec" rid="ss14-1">Section 14.1</xref>).</p>
<p>Each scanned SHS survey field, at the full 0.67-arcsec resolution, contains over 2 Gb of data, so it was not practical to download and compare all the pixel data for each field. Instead, most of the emission variation on a given survey field can be sampled using carefully selected 30-arcmin regions. For 15 fields, several 30-arcmin areas were downloaded to sample the complete dynamic range of emission present. Once the scaling reliability over a range of flux levels and central aperture locations was established, the best single, 30-arcmin region was chosen from the whole frame for the rest of the 233 survey fields to provide the base calibration for each field. The Hα filter flat-field correction was applied to remove the low-level non-uniformities in transmission across the narrow-band filter.</p>
<p>Data requiring a flat-field correction of up to 15 per cent have been shown to be suitable for inclusion in the survey, though in most cases data returned from the SHS web site require less correction than this. For the regions considered here, the pixel data only required flat-field correction ≤3 per cent in most cases and, in general, no more than 8 per cent. For two fields, h350 and h1109 regions well away from the best area of the filter were also selected to confirm that the pixel data behaves as expected when larger flat-field corrections are required. The results are discussed below.</p>
</sec>
<sec id="ss11-4">
<label>11.4</label>
<title>The SHS calibration process</title>
<p>A detailed description of the SHS survey calibration process based on zero-pointing each SHS field to SHASSA is given in the thesis of <xref ref-type="bibr" rid="bib65">Pierce (2005)</xref>. The essentials of this scheme are described here. Each SHS field is completely covered by just one 13° SHASSA field, and data from the best area of SHASSA filter response were chosen for comparison with the SHS images. For direct comparison, the Hα and SR SHS data at 0.67 arcsec was re-binned to match the 48-arcsec SHASSA pixels using the <sc>idl</sc> routine H<sc>rebin</sc>.<xref ref-type="fn" rid="fn5"><sup>5</sup></xref> This returns the mean value of the 72 × 72 full resolution SHS pixels that constitute a single SHASSA 48-arcsec pixel, so the calibration factor determined from the comparison plot applies to the full resolution SHS data. At this coarse resolution, the SR data was scaled and subtracted from the Hα image. Because the correct scaling factor was not yet known, a range of scaling factors from 0.4 to 2.0 was applied so that the best value could be selected by matching the SHASSA zero-point. The equivalent area of SHASSA data was selected, aligned and trimmed to match using the <sc>idl</sc>, <sc>Hastrom</sc> routine. These images were then compared directly, pixel by pixel, with the re-binned, continuum-subtracted SHS data to give a plot of SHASSA values in Rayleighs versus SuperCOSMOS counts per re-binned pixel. The linear portion of the resulting comparison was then fitted to determine the number of SuperCOSMOS counts per 0.67-arcsec pixel per Rayleigh. Averaging SuperCOSMOS data in this way only works properly if all the SuperCOSMOS pixels are on the linear portion of the characteristic curve at the faint end and unsaturated at the bright end. Once the SuperCOSMOS dynamic range is exceeded, pixel saturation arises and the SHASSA to SuperCOSMOS linear relation breaks down as the SuperCOSMOS flux becomes increasingly underestimated (e.g. <xref ref-type="bibr" rid="bib63">Phillipps & Parker 1993</xref>) as seen in <xref ref-type="fig" rid="fig17">Fig. 17</xref>.</p>
<fig id="fig17" position="float">
<label>Figure 17.</label>
<caption><p>The comparison plot for all ten 30-arcmin areas highlighted in <xref ref-type="fig" rid="fig16">Fig. 16</xref>. All align on the one trend, implying no variation in sensitivity across the SHS survey field. The bright photographic saturation is seen from ∼500 Rayleighs. The grey points at the faint end of the plot are taken from the area of poor filter response in the SE corner of h350 and align well with the rest of the data, indicating that, in areas of bright emission, flat-field corrections as large as 20 per cent still return reasonable intensity values.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig017.tif"></graphic>
</fig>
<p>The adopted process was followed for the same 30-arcmin region from SHS field h350 as shown in <xref ref-type="fig" rid="fig13">Fig. 13</xref>. The upper image in <xref ref-type="fig" rid="fig14">Fig. 14</xref> shows the SHS image with the continuum-subtracted at 48-arcsec resolution. The lower image is the trimmed and aligned SHASSA data. Bright stars on the continuum subtracted SHASSA images leave significant residuals, while in the SHS data any stellar residuals are barely visible and then only for the very brightest stars. The pixel-to-pixel comparison plot for this area is shown in <xref ref-type="fig" rid="fig15">Fig. 15</xref>. Each point on this plot is the pixel value from the SuperCOSMOS scan against the Rayleigh value from the SHASSA data. Immediately, it can be seen that the SHS data follow a tight linear relation with the SHASSA values over a range of several hundred Rayleighs. The outliers from this distribution at around 4000 SuperCOSMOS counts correspond to the SHASSA stellar residuals noted from <xref ref-type="fig" rid="fig14">Fig. 14</xref>.</p>
<fig id="fig14" position="float">
<label>Figure 14.</label>
<caption><p>Two Hα images of a 30-arcmin region of SHS field h350 centred on 16<sup>h</sup>47<sup>m</sup>− 49°00″ (J2000) as in <xref ref-type="fig" rid="fig13">Fig. 13</xref>. The top image is the SHS image blocked down to match the 48-arcsec resolution of the SHASSA data and continuum subtracted. The bottom image is the equivalent SHASSA image, trimmed and aligned ready for comparison. Areas of uncancelled bright stars are highlighted.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig014.tif"></graphic>
</fig>
<fig id="fig15" position="float">
<label>Figure 15.</label>
<caption><p>The comparison plot of SHS and SHASSA data from the area shown in <xref ref-type="fig" rid="fig14">Fig. 14</xref>. Each point on the plot is a re-binned pixel value from the SHS data against the Rayleigh value from the SHASSA data. Note the linear relation and the large dynamic range covered by this comparison. The outliers, due to uncancelled bright stars in the SHASSA data, are highlighted.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig015.tif"></graphic>
</fig>
<p>A further nine 30-arcmin areas were examined from field h350 to cover the whole dynamic range of diffuse emission evident in the field. <xref ref-type="fig" rid="fig16">Fig. 16</xref> shows the 16× blocked down Hα image for this field with contours of filter response overlaid and boxes indicating the areas used. The large area of strong emission in the west of this field is caused by the UV flux from OB association Ara 1A A (<xref ref-type="bibr" rid="bib47">Mel'Nik & Efremov 1995</xref>). In all but two cases, the areas were selected from the best area of the filter response, the exception being the two areas extracted from the SE corner which were included to test the effect of using pixel data from the edge of the SHS survey fields where the flat-field correction is larger.</p>
<fig id="fig16" position="float">
<label>Figure 16.</label>
<caption><p>Blocked down image of survey field h350 with overlaid contours at 85, 90, 92, 95 and 97 per cent. The 30-arcmin areas used to make the comparison plot shown in <xref ref-type="fig" rid="fig17">Fig. 17</xref> are framed by the squares, which are drawn in black or white to best contrast with their background. The bright H <sc>ii</sc> region to the right is NGC 6188, excited by the young open cluster NGC 6193, nucleus of Ara OB 1.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig016.tif"></graphic>
</fig>
<p><xref ref-type="fig" rid="fig17">Fig. 17</xref> shows the resulting SHASSA versus SHS comparison plot with differently shaded points belonging to different 30-arcmin areas. Almost the full range of the SHS data is shown, with the pixel values showing a good linear relation to the SHASSA data from the faintest emission on the field at ∼20 Rayleighs right up to ∼500 Rayleighs. The curve in the trend beyond 500 Rayleighs is due to saturation effects with the SHS data. These points were discarded when making the calibration fit.</p>
<p>The reciprocal of the slope of the linear part of the relation provides a calibration factor of 15.1 counts pixel<sup>−1</sup> Rayleigh<sup>−1</sup> to convert the SuperCOSMOS intensity counts to Rayleighs for this field. An estimate of the error in this calibration is possible, based on the vertical scatter of points about this trend as a given SuperCOSMOS value matches a Rayleigh value in this vertical distribution. In this field, the 1σ scatter is 21 Rayleighs.</p>
<p>The data taken from the two areas in the SE corner of the SHS survey field required flat-field correction of up to 20 per cent. They behave very well when compared with the data requiring less correction, neatly overlaying the main trend, with no change in slope or increase in scatter. This justifies the use of the data out to the 15 per cent flat-field contour where the emulsion records strong emission.</p>
</sec>
<sec id="ss11-5">
<label>11.5</label>
<title>SHS sensitivity limit</title>
<p>While the results from field h350 have shown that the survey has been well tuned to the detection of diffuse emission, as well as giving an approximate limit to the point at which the photographic emulsion saturates, the faint limit has not yet been constrained because there is no really faint emission on this field. At the faintest point of 20 Rayleighs, there is no sign of either survey struggling for sensitivity so a field exhibiting fainter emission is required to probe the SHS faint sensitivity limit. According to the SHASSA data, an area of the Southern Galactic Plane in Monoceros harbours diffuse emission that reaches a level as faint as ∼2 Rayleighs, which is ideal to test the faint limit of the SHS data. <xref ref-type="fig" rid="fig18">Fig. 18</xref> shows the 16 times blocked down Hα image of SHS field h1109, which covers this area of sky, with contours of filter response and the areas selected shown as in <xref ref-type="fig" rid="fig16">Fig. 16</xref>. On this field, nine 30-arcmin regions have been examined as two groups: one, labelled 1–5 in <xref ref-type="fig" rid="fig18">Fig. 18</xref>, from the area of best filter response and the other, labelled A-D, probing the combined effects of extremely low levels of emission and decreased filter transmission.</p>
<fig id="fig18" position="float">
<label>Figure 18.</label>
<caption><p>Blocked down SHS Hα image of field h1109 with contours of filter response at 85, 90, 92, 95 and 97 per cent overlaid. Two groups of 30-arcmin areas are marked by squares and labelled to indicate group membership.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig018.tif"></graphic>
</fig>
<p>The comparison plot from the first group is shown in <xref ref-type="fig" rid="fig19">Fig. 19</xref>. Once again, there is a clearly defined relation between the two, although on this faint field the upper saturation limit is not reached. It is immediately obvious that the SHS data can match the SHASSA data right down to the faintest level of emission, although the linear response of the SHS data is difficult to determine at this low level. The SHS data are therefore detecting emission structure as faint as 2 Rayleighs on this field, although this sensitivity is tempered by the scatter evident in the plot and in the examination of the areas from the area of poor filter transmission discussed below. The linear fit returns a value of 7.7 ± 0.1 SuperCOSMOS count pixel<sup>−1</sup> Rayleigh<sup>−1</sup> for this particular field and provides a reasonable calibration as the 1σ scatter to the fit is just 6.2 Rayleighs. Note the factor of 2 difference in the slope of the calibration curve for this low emission level field h1109 (no emission measure greater than about 80 Rayleighs seen in the area considered) compared to that obtained for high emission field h350 in <xref ref-type="fig" rid="fig17">Fig. 17</xref>, which returned 15.1 counts pixel<sup>−1</sup> Rayleigh<sup>−1</sup>, which is closer to that generally obtained for most fields. This serves to emphasize the need for individual field calibration due to the variation in SuperCOSMOS pixel intensities on a given field, arising primarily from variable fog-level, sky background and resulting SuperCOSMOS and emulsion saturation.</p>
<fig id="fig19" position="float">
<label>Figure 19.</label>
<caption><p>Calibration plot of the numbered 30-arcmin areas from the best area of filter response on field h1109. Points from each area are plotted as a different colour. Note the SHS data match the SHASSA data down to the faintest intensity at ∼2 Rayleighs. The linear fit is also plotted.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig019.tif"></graphic>
</fig>
</sec>
<sec id="ss11-6">
<label>11.6</label>
<title>Fifteen fields studied in depth</title>
<p>A total of 15 fields from a wide variety of Galactic environments were studied using several 30-arcmin regions in each in order to build up a global picture of the survey behaviour. The comparison plots for four of these are shown in <xref ref-type="fig" rid="fig20">Fig. 20</xref> with the linear fit overlaid. In each case, a clear, essentially linear relation can be seen between the SHS and SHASSA data. Generally, different 30-arcmin regions follow a single trend, which indicates little variation in emulsion sensitivity across the large SHS images. Three of the fields examined, h175, h350 and h555 show evidence for saturation at the bright end and fix the bright limit at ∼500 to ∼600 Rayleighs, while none of the fields appear to reach the background fog level in the areas that were compared.</p>
<fig id="fig20" position="float">
<label>Figure 20.</label>
<caption><p>Comparison plots for four of the 15 SHS fields that had several 30-arcmin areas tested against SHASSA data. These fields cover varying dynamic ranges so the axes for different fields do not always cover the same dynamic range.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig020.tif"></graphic>
</fig>
</sec>
<sec id="ss11-7">
<label>11.7</label>
<title>Calibration of the entire SHS</title>
<p>From the analysis of the 15 fields considered above, it is clear that each field requires individual calibration and that one, well selected, 30-arcmin area of SHS pixel data can be compared with SHASSA to give a working estimate of the calibration factor and a satisfactory result in most cases. On this basis, the 30-arcmin areas of pixel data which covered the greatest dynamic range of emission were downloaded from each of the 233 SHS fields, re-binned and compared with the equivalent area of SHASSA data. The results for each field can be found on the SHS web site. For each field the position of the area used, the computed scaling factor for continuum subtraction, the linear fit and, where appropriate, the coefficients from a third-degree polynomial fit are given. The 1σ vertical scatter about the linear fit is also quoted to offer an estimate of the error in the calibration. Of the 233 survey fields, 76 are relatively featureless and exhibit little emission. These are difficult to fit and in nine cases the fit failed completely. Forty-three of these show evidence of the low-level photographic fog. Of the remaining 157 fields, 122 are well constrained by a linear fit. For the other 35 fields, the fit can be improved with a low-order polynomial relation. Where this is the case, the coefficients are included in the table on the SHS web site.</p>
</sec>
<sec id="ss11-8">
<label>11.8</label>
<title>Calibration check of SHS field overlap regions</title>
<p>There is generous overlap between survey fields because of the circular aperture of the filter, which allows field-to-field consistency check of the calibration. For six overlap regions between eight fields, a 30-arcmin area was carefully selected from the best possible compromise of filter response between two fields, never requiring flat-field correction greater than 15 per cent. The calibration factor calculated from the field centre in the best region of filter response was applied to these pixel data from the edge. For seven of the eight fields, the calibration factor determined from the linear fit to the data was used. Calibrated and aligned data from the two overlapping SHS fields were plotted pixel by pixel at 0.67, 10 and 48 arcsec resolution. If the independently determined calibration applied to each field is consistent, the resulting plot of Rayleighs from one field against Rayleighs from its neighbour should yield a linear relation with slope of unity and no offset.</p>
<p>From the six fields examined in this way, the results give good agreement. Four examples are shown in <xref ref-type="fig" rid="fig21">Fig. 21</xref> from comparisons at 48-arcsec resolution. Here, the ordinate and abscissa values are in Rayleighs with each axis labelled with its field. The FITS are quoted on the plots and in <xref ref-type="fig" rid="tbl4">Table 4</xref>. Two comparisons, 459–392 and 459–458, agree to better than 10 per cent, three more, 391–329, 458–391 and 460–459 also return linear results but agree to just 14, 29 and 43 per cent, respectively. The bottom three comparisons are for overlapping fields so the good match implies that one could construct seamless, large pixel mosaics. For the h350 and h349, the linear relation is not so well behaved. The slightly curved trend between these two fields probably results from the bright saturation evident in the pixel data of the overlap region used (note the higher Rayleigh limits for this comparison).</p>
<fig id="fig21" position="float">
<label>Figure 21.</label>
<caption><p>Comparisons between adjacent fields that have been calibrated according to a linear fit with SHASSA data.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig021.tif"></graphic>
</fig>
<fig id="tbl4" position="float">
<label>Table 4.</label>
<caption><p>FITS obtained from the comparison of SuperCOSMOS pixel data in overlap regions between adjacent survey fields using linear calibration factors.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-tbl004.tif"></graphic>
</fig>
</sec>
</sec>
<sec id="ss12">
<label>12</label>
<title>Comparison with Iphas</title>
<p>The SHS and IPHAS Hα surveys have areas of overlap at low declinations, which permit a direct comparison to be made between the two complementary surveys. <xref ref-type="fig" rid="fig22">Fig. 22</xref> shows a 3.3 × 2-arcmin region centred on RA 18<sup>h</sup>47<sup>m</sup>42.6<sup>s</sup>, Dec. + 01°33′04″, which includes the newly discovered planetary nebula PHR1847+0132, taken from a slightly shallow SHS survey field h1332 (exposure number HA18088, survey grade A2, but exposure time cut short to 168 min cf. 180 normally). The data have been carefully matched in terms of co-ordinate projection, but not otherwise processed. It is clear that the two surveys achieve similar depth for diffuse emission but that the IPHAS survey goes deeper for point sources due to its better resolution. Further details of the IPHAS survey are given by <xref ref-type="bibr" rid="bib16">Drew et al. (2005)</xref>.</p>
<fig id="fig22" position="float">
<label>Figure 22.</label>
<caption><p>A 3.3 × 2-arcmin comparison region between SHS (top) and IPHAS (bottom) data centred on RT 18<sup>h</sup>47<sup>m</sup>42.6<sup>s</sup>, Dec. + 01°33′04″ including the new planetary nebula PHR1847+0132.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig022.tif"></graphic>
</fig>
</sec>
<sec id="ss13">
<label>13</label>
<title>Colour-Colour Photometric Plots</title>
<p>The SR, Hα‘R-equivalent’ and <italic>I</italic>-magnitudes can be combined to provide Hα−<italic>R</italic> and <italic>R</italic>−<italic>I</italic> colours for the objects detected by the IAM software. The narrow-band Hα photometry should be sensitive to point-source emitters, so the SHS stellar photometry is of particular interest. A CMD of SR magnitude versus Hα−<italic>R</italic> can be constructed from the survey data to trace the average values of Hα−<italic>R</italic> for normal stars by brightness and help identify emitters by highlighting objects that stand apart from this. <xref ref-type="fig" rid="fig23">Fig. 23(a)</xref> shows a CMD constructed from a 1° region from the centre of survey field h135. Most stars can be seen to congregate around a stellar locus running vertically in the diagram at Hα−<italic>R</italic>∼−0.2 and with an increasing spread towards fainter magnitudes. This is due to the census including a more complete population of objects at fainter magnitudes and increasing photon errors. Outliers can be seen either side of the distribution and, if present, emission line objects will sit to the left of the main stellar locus.</p>
<fig id="fig23" position="float">
<label>Figure 23.</label>
<caption><p>The colour-magnitude diagram of SR versus Hα−<italic>R</italic> and the colour-colour plot of <italic>R</italic>−<italic>I</italic> versus Hα−<italic>R</italic> for stars from an area centred on the middle of SHS field h135. On average, the stars sit at roughly neutral values of Hα−<italic>R</italic>=−0.2 and <italic>R</italic>−<italic>I</italic>= 0.15. The reddening in this field of up to <italic>E</italic>(<italic>B</italic>−<italic>V</italic>) = 4.7 mag is evident in the colour-colour plot as a smearing of the stellar locus towards higher values of <italic>R</italic>−<italic>I</italic> and Hα−<italic>R</italic>. The circled point indicates the location of a PNe.</p></caption>
<graphic mimetype="image" xlink:href="362-2-689-fig023.tif"></graphic>
</fig>
<p>A colour-colour plot of <italic>R</italic>−<italic>I</italic> versus Hα−<italic>R</italic> provides more information about the stellar population along a given line of sight. <xref ref-type="fig" rid="fig23">Fig. 23(b)</xref> presents such a plot for the same area of sky as described above and uses the <italic>I</italic>-band magnitudes that have been corrected to the SR photometry. In this plot, the stellar locus is centred at Hα−<italic>R</italic>∼−0.2 and <italic>R</italic>−<italic>I</italic>= 0.15. The area covered suffers high reddening of up to <italic>E</italic>(<italic>B</italic>−<italic>V</italic>) = 4.7 mag (<xref ref-type="bibr" rid="bib73">Schlegel et al. 1998</xref>) and this is evident in the stretching of the stellar locus towards larger values of <italic>R</italic>−<italic>I</italic> and, significantly, Hα−<italic>R</italic>, making them appear to be emission line stars. These reddened non-emitters can be identified in the colour-colour plot of <italic>R</italic>−<italic>I</italic> versus Hα−<italic>R</italic> and excluded from studies of potential point-source emitters (<xref ref-type="bibr" rid="bib65">Pierce 2005</xref>). An additional complication is the potential contamination from late-type stars. A TiO opacity minimum near 6536 Å enables the continuum to be attained, producing the peak, compared to the TiO band heads on either side of the Hα filter. Further to the red, the Tech-Pan emulsion sensitivity cuts off at 6990 Å. Such objects can thus appear as apparent Hα emitters when compared to the matching SR photometry unless the complementary <italic>I</italic>-band photometry is included, as such late type stars will be brighter in this band than Hα emitters. However, colour-colour plots created in 1-degree sub-regions, avoid the smearing effects on the photometry due to small positional shifts in the stellar locus across a Hα survey field. These have proved very effective in identifying point-source emission candidates and has been successfully employed to provide targets for follow-up multi-object spectroscopy with 6dF and 2dF at the AAO (e.g. <xref ref-type="bibr" rid="bib35">Hopewell et al. 2005</xref>).</p>
</sec>
<sec id="ss14">
<label>14</label>
<title>Scientific Exploitation</title>
<p>The SHS online atlas was released in stages starting in 2002 with the complete survey made available in 2003. A variety of programmes are underway to exploit the scientific potential of this new resource. Several illustrative project examples are briefly mentioned below.</p>
<sec id="ss14-1">
<label>14.1</label>
<title>Planetary Nebulae</title>
<p>The largest project arising from the AAO/UKST Hα survey has been the Macquarie/AAO/Strasbourg Hα planetary nebula project (MASH; <xref ref-type="bibr" rid="bib58">Parker et al. 2003</xref>, 2005, in preparation), which has uncovered about 1000 new Galactic PNe, nearly doubling the sample accrued from all sources over the last 100 yr. Related projects concern the identification of a significant new PNe population in the Galactic Bulge (e.g. <xref ref-type="bibr" rid="bib62">Peyaud, Parker & Acker 2003</xref>), and the discovery of an important sample of Wolf-Rayet central stars of PNe (e.g. <xref ref-type="bibr" rid="bib49">Morgan, Parker & Russeil 2001</xref>; <xref ref-type="bibr" rid="bib60">Parker & Morgan 2003</xref>) including the detection of the only [WN] PN central star in the Galaxy (<xref ref-type="bibr" rid="bib50">Morgan, Parker & Cohen 2003</xref>). A possible new phase of PNe evolution has also been reported around a strongly masing OH-IR star (<xref ref-type="bibr" rid="bib9">Cohen, Parker & Chapman 2005</xref>). A very large PN in an early stage of interaction with the ISM has also been discovered (<xref ref-type="bibr" rid="bib66">Pierce et al. 2004</xref>) as well as two, very large bipolar PNe previously misidentified as H <sc>ii</sc> regions (<xref ref-type="bibr" rid="bib20">Frew, Parker & Russeil 2005</xref>). A new sample of large (>4 arcmin), highly evolved, low surface brightness PNe have also been found from examination of 16 × blocked down FITS images of the entire 233 fields of SHS survey. These blocked-down images effectively enhance large angular size low surface brightness features (e.g. <xref ref-type="bibr" rid="bib66">Pierce et al. 2004</xref>, <xref ref-type="bibr" rid="bib20">Frew & Parker 2005</xref>, in preparation). All these discoveries are being investigated with follow-up spectroscopy to determine the fundamental parameters of this significant new sample.</p>
</sec>
<sec id="ss14-2">
<label>14.2</label>
<title>H <sc>ii</sc> regions and regions of star formation</title>
<p>This type of study is currently ripe for exploitation with little work currently undertaken. <xref ref-type="bibr" rid="bib43">Mader et al. (1999)</xref> report the discovery of a significant new population of Herbig-Haro objects from an SHS extension field in Orion and a large wind-blown bubble with secondary star-forming regions around its periphery by <xref ref-type="bibr" rid="bib8">Cohen et al. (2002)</xref>. Numerous very faint H <sc>ii</sc> regions have also been discovered as a by-product of the MASH survey (Parker et al., in preparation). Many large features are evident including bubbles, which trigger star-formation and induce velocity departures of the associated H <sc>ii</sc> regions. Using data from the SHS and additional kinematic information from Fabry-Perot observations (<xref ref-type="bibr" rid="bib23">Georgelin et al. 2000</xref>), the filamentary Hα counterparts and triggered H <sc>ii</sc> regions for the H <sc>i</sc> shell centred at 290.1 + 0.2 (<xref ref-type="bibr" rid="bib68">Rizzo & Arnal 1998</xref>) have been revealed. The high resolution of the data permits precise description of the morphology and extent of such H <sc>ii</sc> regions. This is a vital information in determining the location of the exciting stars, which can be inferred via orientation of the observed rims and dust ‘elephant trunk’ with respect to the H <sc>ii</sc> region as a whole. Furthermore, the Hα counterpart and visible extension can be directly compared to radio H <sc>ii</sc> regions. This is an essential information needed to determine the distance of H <sc>ii</sc> regions in the framework of the study of the large-scale structure of our Galaxy (<xref ref-type="bibr" rid="bib72">Russeil et al. 2005</xref>).</p>
</sec>
<sec id="ss14-3">
<label>14.3</label>
<title>Supernova Remnants</title>
<p>Several programmes searching for the optical counterparts of supernova remnants (SNRs) in the SHS have already been undertaken. <xref ref-type="bibr" rid="bib82">Walker, Zealey & Parker (2001)</xref> report finding new filamentary shell structures traced by Hα emission that are likely associated with Galactic SNRs. A more recent project is underway to uncover SNR candidates across the entire SHS from careful scrutiny of both the blocked-down FITS images and the original survey films, with several new SNRs already confirmed (Stupar et al., in preparation). Searches for new optical Hα counterparts around the known Galactic SNR overlapping the SHS is also underway. One new Galactic SNR discovered serendipitously via the MASH programme has already been reported (<xref ref-type="bibr" rid="bib61">Parker, Frew & Stupar 2004</xref>). A significant increase in the known population of optically detected Galactic SNRs is promised.</p>
</sec>
<sec id="ss14-4">
<label>14.4</label>
<title>Point-source emitters</title>
<p>One area of more recent study is the search for point-source emitters and the subsequent follow-up spectroscopy of candidates identified from the SHS Hα and SR photometry. <xref ref-type="bibr" rid="bib15">Drew et al. (2004)</xref> report the discovery, via SHS photometry, of only the 4th known massive WO star in the Milky Way Galaxy identified as part of a general programme of candidate point-source follow-up. Additionally, <xref ref-type="bibr" rid="bib35">Hopewell et al. (2005)</xref> present five new WC9 stars discovered from the SHS data in a similar fashion. <xref ref-type="bibr" rid="bib65">Pierce (2005)</xref> and <xref ref-type="bibr" rid="bib65">Pierce et al.</xref> (2005, in preparation) demonstrate the power of the SHS to reveal significant new populations of Hα emitters via a particular study in the Vela molecular ridge, especially when combined with <italic>I</italic>-band and 2MASS photometry. These preliminary projects have been finding, for the magnitude range explored most thoroughly (12 < <italic>R</italic> < 16.5), that 10–20 per cent of candidates are confirmed as emission line objects via follow-up spectroscopy. Their Hα equivalent widths usually exceed 20 Å. More recent work by <xref ref-type="bibr" rid="bib65">Pierce (2005)</xref> indicates that the situation can be improved by weeding out M stars more thoroughly using the 2MASS data.</p>
</sec>
</sec>
<sec id="ss15">
<label>15</label>
<title>Conclusions</title>
<p>The AAO/UKST Hα survey as scanned by SuperCOSMOS is now complete and online as the SHS atlas. It represents a powerful tool for the study of the ionized gas content of our Galaxy on a range of spatial scales from arcsecond to tens of degrees. The distribution and structure of the ionized gas result from a wide range of astrophysically interesting phenomena. The astrometric and photometric properties have been described and shown to be well behaved and adequate for most purposes. Importantly, despite difficulties associated with photographic data and the scanning process, comparison with the independently calibrated SHASSA images has shown that the SHS survey faithfully records diffuse Galactic emission over a wide range of intensities from ∼5 Rayleighs to 500 Rayleighs. Emission down to ∼2 Rayleighs has been detected on one field, h1109. A calibration scheme for all 233 survey fields has been generated, based on comparison of a carefully selected, 30 arcmin region from each field with the equivalent area of intensity calibrated SHASSA Hα image. If the limitations of the data are respected in terms of dynamic range, reliable flux estimates are possible. The survey is clearly appropriate for studies of individual Hα emitting objects including point sources as well as being suitable for the study of the ionized ISM in general. A variety of projects exploiting this resource are already underway, and many exciting discoveries have already been made. The community is invited to consider the use of this valuable survey when undertaking any study of the Southern Galactic Plane.</p>
</sec>
</body>
<back>
<ack>
<sec id="ss16">
<title>Acknowledgments</title>
<p>The authors gratefully acknowledge the support of the AAO board, the WFAU at the University of Edinburgh, the Wide-Field Astronomy Panel (UK), the Particle-Physics and Astronomy Research Council and the AAO directors Russell Cannon and Brian Boyle and UKST astronomers-in-charge Ann Savage and Fred Watson for making the SHS survey possible. This paper used comparison data from SHASSA, which was produced with support from the National Science Foundation. MC thanks NASA for supporting his participation in the SHS through LTSA grant NAG5-7936 with UC Berkeley. MJP thanks PPARC for provision of a PhD studentship. We also thank the referee, John Meaburn, for valuable comments on this paper.</p>
</sec>
</ack>
<ref-list>
<title>References</title>
<ref id="bib1">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Arrowsmith</surname><given-names>P.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name></person-group>, <year>2001</year>, <source>Royal Observatory Edinburgh Internal Report, <ext-link ext-link-type="uri" xlink:href="http://www.physics.mg.edu.au/∼gap/papers/">http://www.physics.mg.edu.au/∼gap/papers/</ext-link>(online reference only)</source>
</citation>
</ref>
<ref id="bib2">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Beard</surname><given-names>S. M.</given-names></name><name><surname>MacGillivray</surname><given-names>H. T.</given-names></name><name><surname>Thanisch</surname><given-names>P. F.</given-names></name></person-group>, <year>1990</year>, <source>MNRAS</source>, <volume>247</volume>, <fpage>311</fpage>
</citation>
</ref>
<ref id="bib3">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Bland-Hawthorn</surname><given-names>J. B.</given-names></name><name><surname>Veilleux</surname><given-names>S.</given-names></name><name><surname>Cecil</surname><given-names>G. N.</given-names></name><name><surname>Putman</surname><given-names>M. E.</given-names></name><name><surname>Gibson</surname><given-names>B. K.</given-names></name><name><surname>Maloney</surname><given-names>P. R.</given-names></name></person-group>, <year>1998</year>, <source>MNRAS</source>, <volume>299</volume>, <fpage>611</fpage>
</citation>
</ref>
<ref id="bib4">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Bok</surname><given-names>B. J.</given-names></name><name><surname>Bester</surname><given-names>M. J.</given-names></name><name><surname>Wade</surname><given-names>C. M.</given-names></name></person-group>, <year>1955</year>, <source>Daedalus</source>, <volume>86</volume>, <fpage>9</fpage>
</citation>
</ref>
<ref id="bib5">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Bond</surname><given-names>I. A.</given-names></name><etal></etal></person-group>, <year>2001</year>, <source>MNRAS</source>, <volume>327</volume>, <fpage>868</fpage>
</citation>
</ref>
<ref id="bib6">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Boyle</surname><given-names>B. J.</given-names></name><name><surname>Shanks</surname><given-names>T.</given-names></name><name><surname>Croom</surname><given-names>S. M.</given-names></name></person-group>, <year>1995</year>, <source>MNRAS</source>, <volume>276</volume>, <fpage>33</fpage>
</citation>
</ref>
<ref id="bib7">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Buxton</surname><given-names>M.</given-names></name><name><surname>Bessell</surname><given-names>M.</given-names></name><name><surname>Watson</surname><given-names>B.</given-names></name></person-group>, <year>1998</year>, <source>PASA</source>, <volume>15</volume>, <fpage>24</fpage>
</citation>
</ref>
<ref id="bib8">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Cohen</surname><given-names>M.</given-names></name><name><surname>Green</surname><given-names>A.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Mader</surname><given-names>S.</given-names></name><name><surname>Cannon</surname><given-names>R. D.</given-names></name></person-group>, <year>2002</year>, <source>MNRAS</source>, <volume>336</volume>, <fpage>736</fpage>
</citation>
</ref>
<ref id="bib9">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Cohen</surname><given-names>M.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Chapman</surname><given-names>J.</given-names></name></person-group>, <year>2005</year>, <source>MNRAS</source>, <volume>357</volume>, <fpage>1189</fpage>
</citation>
</ref>
<ref id="bib10">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Croom</surname><given-names>S. M.</given-names></name><name><surname>Ratcliffe</surname><given-names>A.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Shanks</surname><given-names>T.</given-names></name><name><surname>Boyle</surname><given-names>B. J.</given-names></name><name><surname>Smith</surname><given-names>R. J.</given-names></name></person-group>, <year>1999</year>, <source>MNRAS</source>, <volume>306</volume>, <fpage>592</fpage>
</citation>
</ref>
<ref id="bib11">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Davies</surname><given-names>R. D.</given-names></name><name><surname>Elliott</surname><given-names>K. H.</given-names></name><name><surname>Meaburn</surname><given-names>J.</given-names></name></person-group>, <year>1976</year>, <source>Mem. RAS</source>, <volume>81</volume>, <fpage>89</fpage>
</citation>
</ref>
<ref id="bib12">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Dennison</surname><given-names>B.</given-names></name><name><surname>Simonetti</surname><given-names>J. H.</given-names></name><name><surname>Topasna</surname><given-names>G. A.</given-names></name></person-group>, <year>1998</year>, <source>PASA</source>, <volume>15</volume>, <fpage>147</fpage>
</citation>
</ref>
<ref id="bib13">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Dopita</surname><given-names>M. A.</given-names></name><name><surname>Hua</surname><given-names>C. T.</given-names></name></person-group>, <year>1997</year>, <source>ApJS</source>, <volume>108</volume>, <fpage>515</fpage>
</citation>
</ref>
<ref id="bib14">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Dopita</surname><given-names>M. A.</given-names></name><name><surname>Mathewson</surname><given-names>D. S.</given-names></name><name><surname>Ford</surname><given-names>V. L.</given-names></name></person-group>, <year>1985</year>, <source>ApJ</source>, <volume>297</volume>, <fpage>599</fpage>
</citation>
</ref>
<ref id="bib15">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Drew</surname><given-names>J.</given-names></name><name><surname>Barlow</surname><given-names>M. J.</given-names></name><name><surname>Unruh</surname><given-names>Y. C.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Wesson</surname><given-names>R.</given-names></name><name><surname>Pierce</surname><given-names>M. J.</given-names></name><name><surname>Masheder</surname><given-names>M. R. W.</given-names></name><name><surname>Phillipps</surname><given-names>S.</given-names></name></person-group>, <year>2004</year>, <source>MNRAS</source>, <volume>351</volume>, <fpage>206</fpage>
</citation>
</ref>
<ref id="bib16">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Drew</surname><given-names>J.</given-names></name><etal></etal></person-group> <year>2005</year>, <source>MNRAS</source>, submitted
</citation>
</ref>
<ref id="bib17">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Elliot</surname><given-names>K. H.</given-names></name><name><surname>Meaburn</surname><given-names>J.</given-names></name></person-group>, <year>1976</year>, <source>Ap&SS</source>, <volume>39</volume>, <fpage>437</fpage>
</citation>
</ref>
<ref id="bib18">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Elmegreen</surname><given-names>B.</given-names></name><name><surname>Lada</surname><given-names>C. J.</given-names></name></person-group>, <year>1977</year>, <source>ApJ</source>, <volume>214</volume>, <fpage>725</fpage>
</citation>
</ref>
<ref id="bib19">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Finkbeiner</surname><given-names>D. P.</given-names></name></person-group>, <year>2003</year>, <source>ApJS</source>, <volume>146</volume>, <fpage>407</fpage>
</citation>
</ref>
<ref id="bib20">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Frew</surname><given-names>D. J.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Russeil</surname><given-names>D.</given-names></name></person-group> <year>2005</year>, <source>MNRAS</source>, submitted
</citation>
</ref>
<ref id="bib21">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Gaustad</surname><given-names>J. E.</given-names></name><name><surname>McCullough</surname><given-names>P. R.</given-names></name><name><surname>Rosing</surname><given-names>W.</given-names></name><name><surname>van Buren</surname><given-names>D.</given-names></name></person-group>, <year>2001</year>, <source>PASP</source>, <volume>113</volume>, <fpage>1326</fpage>
</citation>
</ref>
<ref id="bib22">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Georgelin</surname><given-names>Y. P.</given-names></name><name><surname>Georgelin</surname><given-names>Y. M.</given-names></name></person-group>, <year>1970</year>, <source>A&AS</source>, <volume>3</volume>, <fpage>1</fpage>
</citation>
</ref>
<ref id="bib23">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Georgelin</surname><given-names>Y. M.</given-names></name><name><surname>Russeil</surname><given-names>D.</given-names></name><name><surname>Amram</surname><given-names>P.</given-names></name><name><surname>Georgelin</surname><given-names>Y. P.</given-names></name><name><surname>Marcelin</surname><given-names>M.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Viale</surname><given-names>A.</given-names></name></person-group>, <year>2000</year>, <source>A&A</source>, <volume>357</volume>, <fpage>c308</fpage>
</citation>
</ref>
<ref id="bib24">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Gerola</surname><given-names>H.</given-names></name><name><surname>Seiden</surname><given-names>P.</given-names></name></person-group>, <year>1978</year>, <source>ApJ</source>, <volume>223</volume>, <fpage>129</fpage>
</citation>
</ref>
<ref id="bib25">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Green</surname><given-names>A. J.</given-names></name><name><surname>Cram</surname><given-names>L. E.</given-names></name><name><surname>Large</surname><given-names>M. I.</given-names></name><name><surname>Ye</surname><given-names>T.</given-names></name></person-group>, <year>1999</year>, <source>ApJS</source>, <volume>122</volume>, <fpage>207</fpage>
</citation>
</ref>
<ref id="bib26">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Gum</surname><given-names>C. S.</given-names></name></person-group>, <year>1952</year>, <source>Observatory</source>, <volume>72</volume>, <fpage>151</fpage>
</citation>
</ref>
<ref id="bib27">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Gum</surname><given-names>C. S.</given-names></name></person-group>, <year>1955</year>, <source>Memoirs RAS</source>, <volume>67</volume>, <fpage>155</fpage>
</citation>
</ref>
<ref id="bib28">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Haffner</surname><given-names>L. M.</given-names></name><name><surname>Reynolds</surname><given-names>R. J.</given-names></name><name><surname>Tufte</surname><given-names>S. L.</given-names></name><name><surname>Madson</surname><given-names>G. J.</given-names></name><name><surname>Jaehnig</surname><given-names>K. P.</given-names></name><name><surname>Percival</surname><given-names>J. W.</given-names></name></person-group>, <year>2003</year>, <source>ApJS</source>, <volume>149</volume>, <fpage>405</fpage>
</citation>
</ref>
<ref id="bib29">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hambly</surname><given-names>N. C.</given-names></name><name><surname>Miller</surname><given-names>L.</given-names></name><name><surname>MacGillivray</surname><given-names>H. T.</given-names></name><name><surname>Herd</surname><given-names>J. T.</given-names></name><name><surname>Cormack</surname><given-names>W. A.</given-names></name></person-group>, <year>1998</year>, <source>MNRAS</source>, <volume>298</volume>, <fpage>897</fpage>
</citation>
</ref>
<ref id="bib30">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hambly</surname><given-names>N. C.</given-names></name><etal></etal></person-group>, <year>2001</year>, <source>MNRAS</source>, <volume>326</volume>, <fpage>1279</fpage>
</citation>
</ref>
<ref id="bib31">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hambly</surname><given-names>N. C.</given-names></name><name><surname>Irwin</surname><given-names>M. J.</given-names></name><name><surname>MacGillivray</surname><given-names>H. T.</given-names></name></person-group>, <year>2001</year>, <source>MNRAS</source>, <volume>326</volume>, <fpage>1295</fpage>
</citation>
</ref>
<ref id="bib32">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hambly</surname><given-names>N. C.</given-names></name><name><surname>Davenhall</surname><given-names>A. C.</given-names></name><name><surname>Irwin</surname><given-names>M. J.</given-names></name><name><surname>MacGillivray</surname><given-names>H. T.</given-names></name></person-group>, <year>2001</year>, <source>MNRAS</source>, <volume>326</volume>, <fpage>1315</fpage>
</citation>
</ref>
<ref id="bib33">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hase</surname><given-names>V. F.</given-names></name><name><surname>Shajn</surname><given-names>G. A.</given-names></name></person-group>, <year>1955</year>, <source>Isv. Krym. Astrofiz. Obs.</source>, <volume>15</volume>, <fpage>11</fpage>
</citation>
</ref>
<ref id="bib34">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hog</surname><given-names>E.</given-names></name><etal></etal></person-group>, <year>2000</year>, <source>A&A</source>, <volume>355</volume>, <fpage>L27</fpage>
</citation>
</ref>
<ref id="bib35">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Hopewell</surname><given-names>E. C.</given-names></name><etal></etal></person-group> <year>2005</year>, <source>MNRAS</source>, in press
</citation>
</ref>
<ref id="bib36">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Jarrett</surname><given-names>T.</given-names></name><name><surname>Chester</surname><given-names>T.</given-names></name><name><surname>Cutri</surname><given-names>R.</given-names></name><name><surname>Schneider</surname><given-names>S.</given-names></name><name><surname>Skrutskie</surname><given-names>M.</given-names></name><name><surname>Huchra</surname><given-names>J. P.</given-names></name></person-group>, <year>2000</year>, <source>AJ</source>, <volume>119</volume>, <fpage>2498</fpage>
</citation>
</ref>
<ref id="bib37">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Johnson</surname><given-names>H. M.</given-names></name></person-group>, <year>1955</year>, <source>ApJ</source>, <volume>121</volume>, <fpage>604</fpage>
</citation>
</ref>
<ref id="bib38">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Johnson</surname><given-names>H. M.</given-names></name></person-group>, <year>1956</year>, <source>ApJ</source>, <volume>124</volume>, <fpage>90</fpage>
</citation>
</ref>
<ref id="bib39">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Keller</surname><given-names>S. C.</given-names></name><name><surname>Grebel</surname><given-names>E. K.</given-names></name><name><surname>Miller</surname><given-names>G. J.</given-names></name><name><surname>Yoss</surname><given-names>K. M.</given-names></name></person-group>, <year>2001</year>, <source>AJ</source>, <volume>122</volume>, <fpage>248</fpage>
</citation>
</ref>
<ref id="bib40">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Kennicutt</surname><given-names>R. C.</given-names></name></person-group>, <year>1992</year>, <source>ApJ</source>, <volume>388</volume>, <fpage>310</fpage>
</citation>
</ref>
<ref id="bib41">
<citation citation-type="book">
<person-group person-group-type="author"><collab>Kodak publication P-315</collab></person-group>, <year>1987</year>, <source>Scientific Imaging with Kodak Films and Plates</source>. <publisher-loc>Eastman Kodak Company</publisher-loc>, <publisher-loc>Rochester NY</publisher-loc>
</citation>
</ref>
<ref id="bib42">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Lasker</surname><given-names>B. M.</given-names></name><etal></etal></person-group>, <year>1988</year>, <source>ApJS</source>, <volume>68</volume>, <fpage>1</fpage>
</citation>
</ref>
<ref id="bib43">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Mader</surname><given-names>S. L.</given-names></name><name><surname>Zealey</surname><given-names>W. J.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Masheder</surname><given-names>M. R. W.</given-names></name></person-group>, <year>1999</year>, <source>MNRAS</source>, <volume>310</volume>, <fpage>331</fpage>
</citation>
</ref>
<ref id="bib44">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Meaburn</surname><given-names>J.</given-names></name></person-group>, <year>1978</year>, <source>Appl. Opt.</source>, <volume>17</volume>, <fpage>1271</fpage>
</citation>
</ref>
<ref id="bib45">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Meaburn</surname><given-names>J.</given-names></name></person-group>, <year>1980</year>, <source>MNRAS</source>, <volume>192</volume>, <fpage>365</fpage>
</citation>
</ref>
<ref id="bib46">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Meaburn</surname><given-names>J.</given-names></name><name><surname>White</surname><given-names>N. J.</given-names></name></person-group>, <year>1982</year>, <source>MNRAS</source>, <volume>200</volume>, <fpage>771</fpage>
</citation>
</ref>
<ref id="bib47">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Mel'Nik</surname><given-names>A. M.</given-names></name><name><surname>Efremov</surname><given-names>Y. N.</given-names></name></person-group>, <year>1995</year>, <source>AstL</source>, <volume>21</volume>, <fpage>10</fpage>
</citation>
</ref>
<ref id="bib48">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Miller</surname><given-names>L.</given-names></name><name><surname>Cormack</surname><given-names>W. A.</given-names></name><name><surname>Paterson</surname><given-names>M. G.</given-names></name><name><surname>Beard</surname><given-names>S. M.</given-names></name><name><surname>Lawrence</surname><given-names>L.</given-names></name></person-group>, <year>1992</year>, in <person-group person-group-type="editor"><name><surname>MacGillivray</surname><given-names>H. T.</given-names></name><name><surname>Thomson</surname><given-names>E. B.</given-names></name></person-group>, eds, <source>Digitised Optical Sky Surveys</source>. <publisher-name>Kluwer</publisher-name>, <publisher-loc>Dordrecht</publisher-loc>, p. <fpage>133</fpage>
</citation>
</ref>
<ref id="bib49">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Morgan</surname><given-names>D. H.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Russeil</surname><given-names>D.</given-names></name></person-group>, <year>2001</year>, <source>MNRAS</source>, <volume>322</volume>, <fpage>877</fpage>
</citation>
</ref>
<ref id="bib50">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Morgan</surname><given-names>D. H.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Cohen</surname><given-names>M.</given-names></name></person-group>, <year>2003</year>, <source>MNRAS</source>, <volume>346</volume>, <fpage>729</fpage>
</citation>
</ref>
<ref id="bib51">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Morgan</surname><given-names>D. H.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name></person-group>, <year>2005</year>, <source>MNRAS</source>, <volume>360</volume>, <fpage>360</fpage>
</citation>
</ref>
<ref id="bib52">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Nossal</surname><given-names>S.</given-names></name><name><surname>Roesler</surname><given-names>F. L.</given-names></name><name><surname>Bishop</surname><given-names>J.</given-names></name><name><surname>Reynolds</surname><given-names>R. J.</given-names></name><name><surname>Haffner</surname><given-names>M.</given-names></name><name><surname>Tufte</surname><given-names>S.</given-names></name><name><surname>Percival</surname><given-names>J.</given-names></name><name><surname>Meirkiewicz</surname><given-names>E. J.</given-names></name></person-group>, <year>2001</year>, <source>J. Geophys. Res</source>., <volume>106</volume>, <fpage>5605</fpage>
</citation>
</ref>
<ref id="bib53">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Osterbrock</surname><given-names>D. E.</given-names></name></person-group>, <year>1989</year>, <source>Astrophysics of Gaseous Nebulae</source>, <publisher-name>University Science Books</publisher-name>
</citation>
</ref>
<ref id="bib54">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Phillipps</surname><given-names>S.</given-names></name></person-group>, <year>1997</year>, <source>PASA</source>, <volume>15</volume>, <fpage>28</fpage>
</citation>
</ref>
<ref id="bib55">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Bland-Hawthorn</surname><given-names>J.</given-names></name></person-group>, <year>1998</year>, <source>PASA</source>, <volume>15</volume>, <fpage>33</fpage>
</citation>
</ref>
<ref id="bib56">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Phillipps</surname><given-names>S.</given-names></name></person-group>, <year>1998</year>, <source>A&G</source>, <volume>39</volume>, <fpage>10</fpage>
</citation>
</ref>
<ref id="bib57">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Malin</surname><given-names>D. F.</given-names></name></person-group>, <year>1999</year>, <source>PASA</source>, <volume>16</volume>, <fpage>288</fpage>
</citation>
</ref>
<ref id="bib58">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Phillipps</surname><given-names>S.</given-names></name></person-group>, <year>2003</year>, in ASP Conf. Ser. Vol. 289, <source>Proceedings of the IAU 8th Asian-Pacific Regional Meeting. Vol. I</source>, Astron. Soc. Pac., San Francisco, p. <fpage>165</fpage>
</citation>
</ref>
<ref id="bib59">
<citation citation-type="other">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><etal></etal></person-group>, <year>2003</year>, in <person-group person-group-type="editor"><name><surname>Dopita</surname><given-names>M.</given-names></name><name><surname>Kwok</surname><given-names>S.</given-names></name><name><surname>Sutherland</surname><given-names>R.</given-names></name></person-group>, eds, <source>ASP Conf. Ser.</source>, Astron. Soc. Pac., San Francisco, p. <fpage>41</fpage>
</citation>
</ref>
<ref id="bib60">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Morgan</surname><given-names>D. H.</given-names></name></person-group>, <year>2003</year>, <source>MNRAS</source>, <volume>341</volume>, <fpage>961</fpage>
</citation>
</ref>
<ref id="bib61">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Frew</surname><given-names>D. J.</given-names></name><name><surname>Stupar</surname><given-names>M.</given-names></name></person-group>, <year>2004</year>, <source>AAO Newslett.</source>, <volume>104</volume>, <fpage>9</fpage>
</citation>
</ref>
<ref id="bib62">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Peyaud</surname><given-names>A. E. J.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Acker</surname><given-names>A.</given-names></name></person-group>, <year>2003</year>, in <source>SF2A-2003: Semaine de l'Astrophysique Francaise</source>. EdP-Sciences Conf. Ser., p.<fpage>311</fpage>
</citation>
</ref>
<ref id="bib63">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Phillipps</surname><given-names>S.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name></person-group>, <year>1993</year>, <source>MNRAS</source>, <volume>265</volume>, <fpage>385</fpage>
</citation>
</ref>
<ref id="bib64">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Pickering</surname><given-names>W. H.</given-names></name></person-group>, <year>1890</year>, <source>Sidereal Messenger</source>, <volume>9</volume>, <fpage>2</fpage>
</citation>
</ref>
<ref id="bib65">
<citation citation-type="other">
<person-group person-group-type="author"><name><surname>Pierce</surname><given-names>M.</given-names></name></person-group>, <year>2005</year>, <source>PhD thesis</source>, Univ. of Bristol
</citation>
</ref>
<ref id="bib66">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Pierce</surname><given-names>M. J.</given-names></name><name><surname>Frew</surname><given-names>D. J.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name><name><surname>Köppen</surname><given-names>J.</given-names></name></person-group>, <year>2004</year>, <source>PASA</source>, <volume>21</volume>, <fpage>334</fpage>
</citation>
</ref>
<ref id="bib67">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Price</surname><given-names>S. D.</given-names></name><name><surname>Egan</surname><given-names>M. P.</given-names></name><name><surname>Carey</surname><given-names>S. J.</given-names></name><name><surname>Mizuno</surname><given-names>D.</given-names></name><name><surname>Kuchar</surname><given-names>T.</given-names></name></person-group>, <year>2001</year>, <source>AJ</source>, <volume>121</volume>, <fpage>2819</fpage>
</citation>
</ref>
<ref id="bib68">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Rizzo</surname><given-names>J. R.</given-names></name><name><surname>Arnal</surname><given-names>E. M.</given-names></name></person-group>, <year>1998</year>, <source>A&A</source>, <volume>332</volume>, <fpage>1025</fpage>
</citation>
</ref>
<ref id="bib69">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Rodgers</surname><given-names>A. W.</given-names></name><name><surname>Campbell</surname><given-names>C. T.</given-names></name><name><surname>Whiteoak</surname><given-names>J. B.</given-names></name></person-group>, <year>1960</year>, <source>MNRAS</source>, <volume>121</volume>, <fpage>103</fpage>
</citation>
</ref>
<ref id="bib70">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Russeil</surname><given-names>D.</given-names></name></person-group>, <year>1997</year>, <source>A&A</source>, <volume>319</volume>, <fpage>788</fpage>
</citation>
</ref>
<ref id="bib71">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Russeil</surname><given-names>D.</given-names></name><name><surname>Georgelin</surname><given-names>Y. M.</given-names></name><name><surname>Amram</surname><given-names>P.</given-names></name><name><surname>Georgelin</surname><given-names>Y. P.</given-names></name><name><surname>Laval</surname><given-names>A.</given-names></name><name><surname>Marcelin</surname><given-names>M.</given-names></name></person-group>, <year>1998</year>, <source>PASA</source>, <volume>15</volume>, <fpage>9</fpage>
</citation>
</ref>
<ref id="bib72">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Russeil</surname><given-names>D.</given-names></name><name><surname>Adami</surname><given-names>C.</given-names></name><name><surname>Amram</surname><given-names>P.</given-names></name><name><surname>Coarer</surname><given-names>E.</given-names></name><name><surname>Georgelin</surname><given-names>T. M.</given-names></name><name><surname>Marcelin</surname><given-names>M.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name></person-group>, <year>2005</year>, <source>A&A</source>, <volume>429</volume>, <fpage>497</fpage>
</citation>
</ref>
<ref id="bib73">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Schlegel</surname><given-names>D. J.</given-names></name><name><surname>Finkbeiner</surname><given-names>D. P.</given-names></name><name><surname>Davis</surname><given-names>M.</given-names></name></person-group>, <year>1998</year>, <source>ApJ</source>, <volume>500</volume>, <fpage>525</fpage>
</citation>
</ref>
<ref id="bib74">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Sharpless</surname><given-names>S.</given-names></name></person-group>, <year>1953</year>, <source>ApJ</source>, <volume>118</volume>, <fpage>362</fpage>
</citation>
</ref>
<ref id="bib75">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Sharpless</surname><given-names>S.</given-names></name></person-group>, <year>1959</year>, <source>ApJS</source>, <volume>4</volume>, <fpage>257</fpage>
</citation>
</ref>
<ref id="bib76">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Sivan</surname><given-names>J. P.</given-names></name></person-group>, <year>1974</year>, <source>A&A</source>, <volume>16</volume>, <fpage>163</fpage>
</citation>
</ref>
<ref id="bib77">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Stephenson</surname><given-names>C. B.</given-names></name><name><surname>Sanduleak</surname><given-names>N.</given-names></name></person-group>, <year>1977</year>, <source>ApJS</source>, <volume>33</volume>, <fpage>459</fpage>
</citation>
</ref>
<ref id="bib78">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Storkey</surname><given-names>A. J.</given-names></name><name><surname>Hambly</surname><given-names>N. C.</given-names></name><name><surname>Williams</surname><given-names>C. K. I.</given-names></name><name><surname>Mann</surname><given-names>R. G.</given-names></name></person-group>, <year>2004</year>, <source>MNRAS</source>, <volume>347</volume>, <fpage>36</fpage>
</citation>
</ref>
<ref id="bib79">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Sung</surname><given-names>H.</given-names></name><name><surname>Chun</surname><given-names>M.</given-names></name><name><surname>Bessell</surname><given-names>M. S.</given-names></name></person-group>, <year>2000</year>, <source>AJ</source>, <volume>120</volume>, <fpage>333</fpage>
</citation>
</ref>
<ref id="bib80">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Tenorio-Tagle</surname><given-names>G.</given-names></name><name><surname>Palous</surname><given-names>J.</given-names></name></person-group>, <year>1987</year>, <source>A&A</source>, <volume>186</volume>, <fpage>287</fpage>
</citation>
</ref>
<ref id="bib81">
<citation citation-type="book">
<person-group person-group-type="author"><name><surname>Tritton</surname><given-names>S. B.</given-names></name></person-group>, <year>1983</year>, <source>UKSTU Handboook</source>, Publication of the Royal Observatory Edinburgh
</citation>
</ref>
<ref id="bib82">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Walker</surname><given-names>A.</given-names></name><name><surname>Zealey</surname><given-names>W. J.</given-names></name><name><surname>Parker</surname><given-names>Q. A.</given-names></name></person-group>, <year>2001</year>, <source>PASA</source>, <volume>18</volume>, <fpage>259</fpage>
</citation>
</ref>
<ref id="bib83">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Watson</surname><given-names>F. G.</given-names></name></person-group>, <year>1984</year>, <source>MNRAS</source>, <volume>206</volume>, <fpage>661</fpage>
</citation>
</ref>
<ref id="bib84">
<citation citation-type="journal">
<person-group person-group-type="author"><name><surname>Zacharias</surname><given-names>N.</given-names></name><name><surname>Urban</surname><given-names>S. E.</given-names></name><name><surname>Zacharias</surname><given-names>M. I.</given-names></name><name><surname>Wycoff</surname><given-names>G. L.</given-names></name><name><surname>Hall</surname><given-names>D. M.</given-names></name><name><surname>Monet</surname><given-names>D. G.</given-names></name><name><surname>Raffert</surname><given-names>T. J.</given-names></name></person-group>, <year>2004</year>, <source>AJ</source>, <volume>127</volume>, <fpage>3043</fpage>
</citation>
</ref>
</ref-list>
<fn-group>
<fn id="fn1" fn-type="other">
<label>1</label><p><ext-link ext-link-type="uri" xlink:href="http://www-wfau.roe.ac.uk/sss/halpha/">http://www-wfau.roe.ac.uk/sss/halpha/</ext-link></p>
</fn>
<fn id="fn2" fn-type="other">
<label>2</label><p><ext-link ext-link-type="uri" xlink:href="http://surveys.roe.ac.uk/ssa/hablock/hafull.html">http://surveys.roe.ac.uk/ssa/hablock/hafull.html</ext-link></p>
</fn>
<fn id="fn3" fn-type="other">
<label>3</label><p><ext-link ext-link-type="uri" xlink:href="http://www-wfau.roe.ac.uk/sss/halpha">http://www-wfau.roe.ac.uk/sss/halpha</ext-link></p>
</fn>
<fn id="fn4" fn-type="other">
<label>4</label><p><ext-link ext-link-type="uri" xlink:href="http://amundsen.swarthmore.edu/SHASSA/">http://amundsen.swarthmore.edu/SHASSA/</ext-link></p>
</fn>
<fn id="fn5" fn-type="other">
<label>5</label><p>Interactive Data Language: <ext-link ext-link-type="uri" xlink:href="http://www.rsinc.com">http://www.rsinc.com</ext-link></p>
</fn>
</fn-group>
</back>
</article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>The AAO/UKST SuperCOSMOS Hα survey</title></titleInfo><titleInfo type="alternative" contentType="CDATA"><title>The AAO/UKST SuperCOSMOS Hα survey</title></titleInfo><name type="personal" displayLabel="corresp"><namePart type="given">Quentin A.</namePart><namePart type="family">Parker</namePart><affiliation>Macquarie University, Sydney, Australia</affiliation><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation><affiliation>E-mail: qap@ics.mq.edu.au</affiliation><affiliation></affiliation><affiliation>E-mail: qap@ics.mq.edu.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">S.</namePart><namePart type="family">Phillipps</namePart><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">M. J.</namePart><namePart type="family">Pierce</namePart><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">M.</namePart><namePart type="family">Hartley</namePart><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">N. C.</namePart><namePart type="family">Hambly</namePart><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">M. A.</namePart><namePart type="family">Read</namePart><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">H. T.</namePart><namePart type="family">MacGillivray</namePart><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">S. B.</namePart><namePart type="family">Tritton</namePart><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">C. P.</namePart><namePart type="family">Cass</namePart><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">R. D.</namePart><namePart type="family">Cannon</namePart><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">M.</namePart><namePart type="family">Cohen</namePart><affiliation>UC, Berkeley, USA</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">J. E.</namePart><namePart type="family">Drew</namePart><affiliation>Imperial College, London</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">D. J.</namePart><namePart type="family">Frew</namePart><affiliation>Macquarie University, Sydney, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">E.</namePart><namePart type="family">Hopewell</namePart><affiliation>Imperial College, London</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">S.</namePart><namePart type="family">Mader</namePart><affiliation>Australia Telescope National Facility, Parkes, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">D. F.</namePart><namePart type="family">Malin</namePart><affiliation>Anglo-Australian Observatory, Epping, New South Wales, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">M. R. W.</namePart><namePart type="family">Masheder</namePart><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">D. H.</namePart><namePart type="family">Morgan</namePart><affiliation>Institute for Astronomy, School of Physics, University of Edinburgh, Edinburgh</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">R. A. H.</namePart><namePart type="family">Morris</namePart><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">D.</namePart><namePart type="family">Russeil</namePart><affiliation>Observatoire de Marseille, 2 Place le Verrier, Marseille, 13248 cedex 4, France</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">K. S.</namePart><namePart type="family">Russell</namePart><affiliation>UK Schmidt Telescope, Anglo-Australian Observatory, Siding Spring, New South Wales, Australia</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">R. N. F.</namePart><namePart type="family">Walker</namePart><affiliation>Astrophysics Group, University of Bristol, Tyndall Avenue, Bristol</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="research-article" authority="ISTEX" authorityURI="https://content-type.data.istex.fr" valueURI="https://content-type.data.istex.fr/ark:/67375/XTP-1JC4F85T-7">research-article</genre><originInfo><publisher>Blackwell Science Ltd</publisher><place><placeTerm type="text">Oxford, UK</placeTerm></place><dateIssued encoding="w3cdtf">2005-09-11</dateIssued><copyrightDate encoding="w3cdtf">2005</copyrightDate></originInfo><abstract>The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band Hα plus [N ii] 6548, 6584-Å survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Hα Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.</abstract><subject lang="en"><genre>Key words</genre><topic>astronomical data bases: miscellaneous</topic><topic>catalogues</topic><topic>surveys</topic><topic>stars: emission line</topic><topic>photometry</topic></subject><relatedItem type="host"><titleInfo><title>Monthly Notices of the Royal Astronomical Society</title></titleInfo><titleInfo type="abbreviated"><title>Mon. Not. R. Astron. Soc.</title></titleInfo><genre type="journal" authority="ISTEX" authorityURI="https://publication-type.data.istex.fr" valueURI="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</genre><identifier type="ISSN">0035-8711</identifier><identifier type="eISSN">1365-2966</identifier><identifier type="PublisherID">mnras</identifier><identifier type="PublisherID-hwp">mnras</identifier><part><date>2005</date><detail type="volume"><caption>vol.</caption><number>362</number></detail><detail type="issue"><caption>no.</caption><number>2</number></detail><extent unit="pages"><start>689</start><end>710</end></extent></part></relatedItem><identifier type="istex">D6276BED7D62FB067443F2193817ECCDA3997AC7</identifier><identifier type="DOI">10.1111/j.1365-2966.2005.09350.x</identifier><accessCondition type="use and reproduction" contentType="copyright">© 2005 RAS</accessCondition><recordInfo><recordContentSource authority="ISTEX" authorityURI="https://loaded-corpus.data.istex.fr" valueURI="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-GTWS0RDP-M">oup</recordContentSource><recordOrigin>© 2005 RAS</recordOrigin></recordInfo></mods><json:item><extension>json</extension><original>false</original><mimetype>application/json</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/metadata/json</uri></json:item></metadata><annexes><json:item><extension>jpeg</extension><original>true</original><mimetype>image/jpeg</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/annexes/jpeg</uri></json:item><json:item><extension>gif</extension><original>true</original><mimetype>image/gif</mimetype><uri>https://api.istex.fr/document/D6276BED7D62FB067443F2193817ECCDA3997AC7/annexes/gif</uri></json:item></annexes><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Wicri/Asie/explor/AustralieFrV1/Data/Istex/Corpus
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 002797 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Istex/Corpus/biblio.hfd -nk 002797 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien
|wiki= Wicri/Asie
|area= AustralieFrV1
|flux= Istex
|étape= Corpus
|type= RBID
|clé= ISTEX:D6276BED7D62FB067443F2193817ECCDA3997AC7
|texte= The AAO/UKST SuperCOSMOS Hα survey
}}
| This area was generated with Dilib version V0.6.33. |  |