Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing
Identifieur interne : 000115 ( Istex/Corpus ); précédent : 000114; suivant : 000116Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing
Auteurs : Geraint F. Lewis ; Rodrigo A. Ibata ; Sara L. Ellison ; Bastien Aracil ; Patrick Petitjean ; Max Pettini ; Raghunathan SrianandSource :
- Monthly Notices of the Royal Astronomical Society [ 0035-8711 ] ; 2002-07-21.
Abstract
While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.
Url:
DOI: 10.1046/j.1365-8711.2002.05700.x
Links to Exploration step
ISTEX:0644AA2C1BDB1911D5BF828A66A06779528BEA1CLe document en format XML
<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title><author><name sortKey="Lewis, Geraint F" sort="Lewis, Geraint F" uniqKey="Lewis G" first="Geraint F." last="Lewis">Geraint F. Lewis</name><affiliation><mods:affiliation>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Ibata, Rodrigo A" sort="Ibata, Rodrigo A" uniqKey="Ibata R" first="Rodrigo A." last="Ibata">Rodrigo A. Ibata</name><affiliation><mods:affiliation>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Ellison, Sara L" sort="Ellison, Sara L" uniqKey="Ellison S" first="Sara L." last="Ellison">Sara L. Ellison</name><affiliation><mods:affiliation>European Southern Observatory, Casilla 19001, Santiago 19, Chile</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Aracil, Bastien" sort="Aracil, Bastien" uniqKey="Aracil B" first="Bastien" last="Aracil">Bastien Aracil</name><affiliation><mods:affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Petitjean, Patrick" sort="Petitjean, Patrick" uniqKey="Petitjean P" first="Patrick" last="Petitjean">Patrick Petitjean</name><affiliation><mods:affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Pettini, Max" sort="Pettini, Max" uniqKey="Pettini M" first="Max" last="Pettini">Max Pettini</name><affiliation><mods:affiliation>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Srianand, Raghunathan" sort="Srianand, Raghunathan" uniqKey="Srianand R" first="Raghunathan" last="Srianand">Raghunathan Srianand</name><affiliation><mods:affiliation>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:0644AA2C1BDB1911D5BF828A66A06779528BEA1C</idno><date when="2002" year="2002">2002</date><idno type="doi">10.1046/j.1365-8711.2002.05700.x</idno><idno type="url">https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">000115</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">000115</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title><author><name sortKey="Lewis, Geraint F" sort="Lewis, Geraint F" uniqKey="Lewis G" first="Geraint F." last="Lewis">Geraint F. Lewis</name><affiliation><mods:affiliation>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Ibata, Rodrigo A" sort="Ibata, Rodrigo A" uniqKey="Ibata R" first="Rodrigo A." last="Ibata">Rodrigo A. Ibata</name><affiliation><mods:affiliation>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Ellison, Sara L" sort="Ellison, Sara L" uniqKey="Ellison S" first="Sara L." last="Ellison">Sara L. Ellison</name><affiliation><mods:affiliation>European Southern Observatory, Casilla 19001, Santiago 19, Chile</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Aracil, Bastien" sort="Aracil, Bastien" uniqKey="Aracil B" first="Bastien" last="Aracil">Bastien Aracil</name><affiliation><mods:affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Petitjean, Patrick" sort="Petitjean, Patrick" uniqKey="Petitjean P" first="Patrick" last="Petitjean">Patrick Petitjean</name><affiliation><mods:affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Pettini, Max" sort="Pettini, Max" uniqKey="Pettini M" first="Max" last="Pettini">Max Pettini</name><affiliation><mods:affiliation>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation></author><author><name sortKey="Srianand, Raghunathan" sort="Srianand, Raghunathan" uniqKey="Srianand R" first="Raghunathan" last="Srianand">Raghunathan Srianand</name><affiliation><mods:affiliation>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: gfl@aaoepp.aao.gov.au</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><date type="published" when="2002-07-21">2002-07-21</date><biblScope unit="volume">334</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="L7">L7</biblScope><biblScope unit="page" to="L10">L10</biblScope></imprint><idno type="ISSN">0035-8711</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0035-8711</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract">While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.</div></front></TEI><istex><corpusName>oup</corpusName><author><json:item><name>Geraint F. Lewis</name><affiliations><json:string>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Rodrigo A. Ibata</name><affiliations><json:string>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Sara L. Ellison</name><affiliations><json:string>European Southern Observatory, Casilla 19001, Santiago 19, Chile</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Bastien Aracil</name><affiliations><json:string>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Patrick Petitjean</name><affiliations><json:string>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Max Pettini</name><affiliations><json:string>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item><json:item><name>Raghunathan Srianand</name><affiliations><json:string>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string><json:string>E-mail: gfl@aaoepp.aao.gov.au</json:string></affiliations></json:item></author><subject><json:item><value>gravitational lensing</value></json:item><json:item><value>quasars: individual: APM08279+5255</value></json:item></subject><arkIstex>ark:/67375/HXZ-K7NG4K53-4</arkIstex><language><json:string>unknown</json:string></language><originalGenre><json:string>research-article</json:string></originalGenre><abstract>While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.</abstract><qualityIndicators><score>7.123</score><pdfWordCount>3275</pdfWordCount><pdfCharCount>18366</pdfCharCount><pdfVersion>1.4</pdfVersion><pdfPageCount>4</pdfPageCount><pdfPageSize>612 x 792 pts (letter)</pdfPageSize><refBibsNative>true</refBibsNative><abstractWordCount>154</abstractWordCount><abstractCharCount>1067</abstractCharCount><keywordCount>2</keywordCount></qualityIndicators><title>Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</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>334</volume><issue>1</issue><pages><first>L7</first><last>L10</last></pages><genre><json:string>journal</json:string></genre></host><namedEntities><unitex><date><json:string>2002</json:string></date><geogName></geogName><orgName></orgName><orgName_funder></orgName_funder><orgName_provider></orgName_provider><persName><json:string>Rodrigo A. Ibata</json:string><json:string>F. Lewis</json:string><json:string>Max Pettini</json:string><json:string>Bastien Aracil</json:string><json:string>A. Estimates</json:string><json:string>Sara L. Ellison</json:string><json:string>Patrick Petitjean</json:string><json:string>C. Section</json:string></persName><placeName><json:string>Paris</json:string><json:string>Chile</json:string><json:string>Canada</json:string><json:string>India</json:string><json:string>Pune</json:string><json:string>Strasbourg</json:string><json:string>France</json:string></placeName><ref_url><json:string>http://wise-obs.tau.ac.il/</json:string></ref_url><ref_bibl><json:string>Ibata et al. (1999)</json:string><json:string>Lewis et al. 1998b</json:string><json:string>Saust 1994</json:string><json:string>Petitjean et al. 2000</json:string><json:string>Ellison et al. 1999a,b</json:string><json:string>Ibata et al. 1999</json:string><json:string>Lewis et al. 1998a</json:string><json:string>Lewis et al. (2002)</json:string><json:string>Irwin et al. 1998</json:string><json:string>Burke 1981</json:string><json:string>Srianand & Petitjean 2000</json:string><json:string>Ledoux et al. 1998</json:string><json:string>Bartelmann & Loeb 1998</json:string><json:string>Lewis et al. (1998b)</json:string><json:string>Egami et al. (2000)</json:string><json:string>G. F. Lewis et al.</json:string><json:string>Munoz et al. (2001)</json:string><json:string>Lewis et al. 2002</json:string><json:string>Nemiroff 1988</json:string><json:string>Munoz, Kochanek & Keeton 2001</json:string><json:string>Schneider & Wambsganss 1990</json:string><json:string>Egami et al. 2000</json:string><json:string>Munoz et al. 2001</json:string><json:string>Francis et al. 1991</json:string></ref_bibl><bibl></bibl></unitex></namedEntities><ark><json:string>ark:/67375/HXZ-K7NG4K53-4</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></categories><publicationDate>2002</publicationDate><copyrightDate>2002</copyrightDate><doi><json:string>10.1046/j.1365-8711.2002.05700.x</json:string></doi><id>0644AA2C1BDB1911D5BF828A66A06779528BEA1C</id><score>1</score><fulltext><json:item><extension>pdf</extension><original>true</original><mimetype>application/pdf</mimetype><uri>https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/fulltext/pdf</uri></json:item><json:item><extension>zip</extension><original>false</original><mimetype>application/zip</mimetype><uri>https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a">Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher scheme="https://publisher-list.data.istex.fr">Blackwell Science Ltd</publisher><availability><licence><p>© 2002 RAS</p></licence><p scheme="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-GTWS0RDP-M">oup</p></availability><date>2002</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">Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title><author xml:id="author-0000" corresp="yes"><persName><forename type="first">Geraint F.</forename><surname>Lewis</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</affiliation></author><author xml:id="author-0001" corresp="yes"><persName><forename type="first">Rodrigo A.</forename><surname>Ibata</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</affiliation></author><author xml:id="author-0002" corresp="yes"><persName><forename type="first">Sara L.</forename><surname>Ellison</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>European Southern Observatory, Casilla 19001, Santiago 19, Chile</affiliation></author><author xml:id="author-0003" corresp="yes"><persName><forename type="first">Bastien</forename><surname>Aracil</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</affiliation></author><author xml:id="author-0004" corresp="yes"><persName><forename type="first">Patrick</forename><surname>Petitjean</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</affiliation></author><author xml:id="author-0005" corresp="yes"><persName><forename type="first">Max</forename><surname>Pettini</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</affiliation></author><author xml:id="author-0006" corresp="yes"><persName><forename type="first">Raghunathan</forename><surname>Srianand</surname></persName><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><email>gfl@aaoepp.aao.gov.au</email><affiliation>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</affiliation></author><idno type="istex">0644AA2C1BDB1911D5BF828A66A06779528BEA1C</idno><idno type="ark">ark:/67375/HXZ-K7NG4K53-4</idno><idno type="DOI">10.1046/j.1365-8711.2002.05700.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><date type="published" when="2002-07-21"></date><biblScope unit="volume">334</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="L7">L7</biblScope><biblScope unit="page" to="L10">L10</biblScope></imprint></monogr></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2002</date></creation><abstract><p>While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.</p></abstract><textClass><keywords scheme="keyword"><list><head>Key words</head><item><term>gravitational lensing</term></item><item><term>quasars: individual: APM08279+5255</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2002-07-21">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/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>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1046/j.1365-8711.2002.05700.x</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Letters</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes">
<name><surname>Lewis</surname><given-names>Geraint F.</given-names></name><xref ref-type="aff" rid="au1">1</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Ibata</surname><given-names>Rodrigo A.</given-names></name><xref ref-type="aff" rid="au2">2</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Ellison</surname><given-names>Sara L.</given-names></name><xref ref-type="aff" rid="au3">3</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Aracil</surname><given-names>Bastien</given-names></name><xref ref-type="aff" rid="au4">4</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Petitjean</surname><given-names>Patrick</given-names></name><xref ref-type="aff" rid="au4">4</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Pettini</surname><given-names>Max</given-names></name><xref ref-type="aff" rid="au5">5</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Srianand</surname><given-names>Raghunathan</given-names></name><xref ref-type="aff" rid="au6">6</xref><xref ref-type="corresp" rid="cor1">⋆</xref>
</contrib>
<aff id="au1"><label>1</label>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</aff>
<aff id="au2"><label>2</label>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</aff>
<aff id="au3"><label>3</label>European Southern Observatory, Casilla 19001, Santiago 19, Chile</aff>
<aff id="au4"><label>4</label>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</aff>
<aff id="au5"><label>5</label>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</aff>
<aff id="au6"><label>6</label>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</aff>
</contrib-group>
<author-notes>
<corresp id="cor1">
<label>⋆</label>E-mail: <email>gfl@aaoepp.aao.gov.au</email> (GFL); <email>ibata@pleiades.u-strasbg.fr</email> (RAI); <email>sellison@eso.org</email> (SLE); <email>aracil@iap.fr</email> (BA); <email>petitjean@iap.fr</email> (PP); <email>pettini@ast.cam.ac.uk</email> (MP); <email>anand@iucaa.ernet.in</email> (RS)</corresp>
</author-notes>
<pub-date pub-type="ppub">
<day>21</day>
<month>7</month>
<year>2002</year>
</pub-date>
<volume>334</volume>
<issue>1</issue>
<fpage>L7</fpage>
<lpage>L10</lpage>
<history>
<date date-type="received"><day>24</day><month>4</month><year>2002</year></date>
<date date-type="accepted"><day>17</day><month>5</month><year>2002</year></date>
</history>
<permissions>
<copyright-statement>© 2002 RAS</copyright-statement>
<copyright-year>2002</copyright-year>
</permissions>
<abstract>
<title>Abstract</title>
<p>While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the <italic>Hubble Space Telescope</italic> (<italic>HST</italic>), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.</p>
</abstract>
<kwd-group>
<title>Key words:</title>
<kwd>gravitational lensing</kwd>
<kwd>quasars: individual: APM08279+5255</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec id="ss1">
<title>1 INTRODUCTION</title>
<p>The <italic>z</italic>= 3.911 broad absorption line (BAL) quasar APM08279+5255 was identified serendipitously within a survey of carbon stars in the Galactic halo (<xref ref-type="bibr" rid="bib8">Irwin et al. 1998</xref>). The optical emission is coincident with a ∼1-Jy <italic>IRAS</italic> source at 100 μm and was also found to be a significant submillimetre source, with a flux of 75 mJy at 850 μm (<xref ref-type="bibr" rid="bib11">Lewis et al. 1998a</xref>); the inferred bolometric luminosity is ∼5 × 10<sup>15</sup> L<sub>⊙</sub>, making APM08279+5255 one of the most luminous sources known. The discovery images revealed that APM08279+5255 is not a single point-like source, rather it is extended (<xref ref-type="bibr" rid="bib8">Irwin et al. 1998</xref>). Adaptive optics with the Canada–France–Hawaii Telescope (CFHT) clearly displayed the compound nature of APM08279+5255, revealing a pair of point-like images separated by 0.4 arcsec (<xref ref-type="bibr" rid="bib9">Ledoux et al. 1998</xref>). Further observations, using NICMOS on the <italic>Hubble Space Telescope</italic> (<italic>HST</italic>) (<xref ref-type="bibr" rid="bib7">Ibata et al. 1999</xref>) and the Keck telescope (<xref ref-type="bibr" rid="bib3">Egami et al. 2000</xref>), uncovered a fainter third image between the brighter two, the colours of which suggest that it represents a third image of the quasar.</p>
<p>Paradoxically, this conclusion is somewhat problematic. Although one of the fundamental predictions of gravitational lens theory is that there should always be an odd number of lensed images (e.g. <xref ref-type="bibr" rid="bib2">Burke 1981</xref>), in practice all lensed quasi-stellar objects (QSOs) known to date exhibit an even number of images. <xref ref-type="bibr" rid="bib15">Narasimha, Subramanian & Chitre (1986)</xref> have shown that this is in fact expected if the lensing galaxies have very small core radii; the core ‘captures’ one of the images and strongly demagnifies it. The fact that APM08279+5255 apparently defies this trend is reflected in the mass models for the lens which require unphysically large cores to explain the brightness of image C, if the latter is indeed an image of the QSO (<xref ref-type="bibr" rid="bib7">Ibata et al. 1999</xref>; <xref ref-type="bibr" rid="bib3">Egami et al. 2000</xref>; <xref ref-type="bibr" rid="bib14">Munoz, Kochanek & Keeton 2001</xref>). This led <xref ref-type="bibr" rid="bib7">Ibata et al. (1999)</xref> to also propose an alternative model where component C is actually the lensing galaxy responsible for the observed configuration; this model possesses more ‘typical’ galaxy parameters. Recent observations of the nuclear CO(1-0) emission in APM08279+5255 reveals a complex morphology which suggests that the lens in this system is a highly flattened system, such as an edge-on spiral galaxy (<xref ref-type="bibr" rid="bib13">Lewis et al. 2002</xref>). With this model, component C is an image of the quasar and the ternary configuration of the quasar source lying in the vicinity of a ‘naked cusp’ (e.g. <xref ref-type="bibr" rid="bib1">Bartelmann & Loeb 1998</xref>).</p>
<p>The situation is complicated by the presence of two very strong Mg <sub>ii</sub> systems at <italic>z</italic>= 1.062 and 1.181. A detailed study of the corresponding absorption spectrum shows that these systems are damped with a very high H <sub>i</sub> column density (<10<sup>21</sup> cm<sup>−2</sup>; <xref ref-type="bibr" rid="bib17">Petitjean et al. 2000</xref>). The objects associated with these two systems could both contribute to the lensing of the quasar.</p>
<p>Given the extreme apparent properties of APM08279+5255, an accurate lens model is essential for the determination of its true intrinsic properties. This paper presents new spatially resolved spectra of the various components in this lensing system, with the goal of determining the nature of component C. Section 2 presents a description of the observing and data reduction, reviewing the nature of component C in Section 3. This section also discusses the implications of this study. Finally, the conclusions are presented in Section 4.</p>
</sec>
<sec id="ss2">
<title>2 OBSERVATIONS AND REDUCTION</title>
<sec id="ss2-1">
<title>2.1 Observations</title>
<p>The aim of the observing program was to obtain a spatially resolved, high resolution spectrum of the <italic>z</italic>= 3.911 BAL quasar, APM08279+5255. While being triply imaged, the image separations in this system are small, ranging from 0.15 arcsec to a maximum of 0.38 arcsec. Ground-based observations of this bright source have revealed a rich absorption spectrum caused by both intervening material and the complex QSO environment (<xref ref-type="bibr" rid="bib4">Ellison et al. 1999a</xref>,<xref ref-type="bibr" rid="bib5">b</xref>; <xref ref-type="bibr" rid="bib20">Srianand & Petitjean 2000</xref>; <xref ref-type="bibr" rid="bib17">Petitjean et al. 2000</xref>).</p>
<p>The Space Telescope Imaging Spectrograph (STIS) on-board the <italic>HST</italic> was employed in this endeavour. The principal aim was to probe the numerous intervening systems on sub-kpc scales, to investigate the structure of intervening galaxy haloes and metal line systems on scales of ∼0.2–1.6 kpc h<sup>−1</sup>, as well as their kinematics and spatial extents. A further goal was to obtain multiple sightlines through the complex BAL flow on parsec scales, yielding information on ionization, kinematics and metal enrichment; these will be the topics of forthcoming articles. Here we present an initial investigation of the spectra in the individual lensed images, with the goal of establishing the nature of image C.</p>
<p>The STIS G750M grating was used in five different (primary) wavelength settings so as to achieve complete coverage from ∼6000–8600Å (see <xref ref-type="fig" rid="tbl001">Table 1</xref>). Acquisition was achieved using the brightest component A. The 52 × 0.2 arcsec slit was then oriented along the major axis between the two brightest components (A and B) and then offset perpendicularly by 0.02 arcsec to achieve improved centring on the faint component C. The STIS spatial pixel scale is 0.051 arcsec pixel<sup>−1</sup>, with a typical dispersion of 0.56Å pixel<sup>−1</sup>. In addition to the standard calibrations (including spectra of the HeAr arc lamp for wavelength calibration), extra flat field images were obtained for the three reddest settings in order to correct for significant fringing at these wavelengths. Multiple exposures were obtained for each setting, subsequent exposures stepped along the slit by 1 arcsec.</p>
<fig id="tbl001" position="anchor">
<label>1</label>
<caption><p>Summary of observations.</p></caption>
<graphic mimetype="image" xlink:href="334-1-L7-tbl001.tif"></graphic>
</fig>
<p>Due to a combination of narrow scheduling windows and backlog from previous cycles, only a subset of the orbits has so far been completed, see <xref ref-type="fig" rid="tbl001">Table 1</xref>. While we defer a comprehensive analysis of the absorption spectra until the full data set has been acquired, there is sufficient information in the first wavelength setting, at λ<sub>central</sub>= 6252Å (first line of <xref ref-type="fig" rid="tbl001">Table 1</xref>) to confirm the nature of component C. The data considered in this paper consist of five individual spectroscopic exposures; each exposure was offset by 20 pixels (1 arcsec) relative to the previous one, so as to maintain optimal spatial resolution and minimize the effects of CCD and camera artifacts.</p>
</sec>
<sec id="ss2-2">
<title>2.2 Data reduction</title>
<p>The extraction of the individual spectra is slightly complicated by the fact that the spectra are not completely separated, especially components A and C, even with the superb resolution afforded by STIS. The extraction was performed in a straightforward, but non-standard way, which we now detail. The adopted procedure is similar to that undertaken for the complex gravitational lens Q2237+0305 by <xref ref-type="bibr" rid="bib11">Lewis et al. (1998b)</xref>.</p>
<p>The first step we took was to trace the spectrum of of component A (the brightest QSO component) with a straight line fit; this gives the spatial offset between the spectral images to ∼0.02 pixels. After correcting for the slope of the spectrum on the image, we obtain the distribution of flux in the spatial direction, integrated over the wavelength range, 5965 to 6534Å (<xref ref-type="fig" rid="fig001">Fig. 1</xref>). To aid the visual interpretation of this diagram, we have overlaid a three component Gaussian fit. The three quasar components are clearly distinguished in this single spectroscopic exposure; also evident is the peculiar asymmetric profile (seen as an excess over the Gaussian fit to the left side of components A and B).</p>
<fig id="fig001" position="anchor">
<label>1</label>
<caption>
<p>Flux distribution along the spatial direction of the slit. From left to right, the peaks correspond to images A, C and B. The three component Gaussian fit is displayed with a dotted line, and the dashed line shows the sum of the three Gaussians.</p>
</caption>
<graphic mimetype="image" xlink:href="334-1-L7-fig001.gif"></graphic>
</fig>
<p>We constructed a model point-spread function using an archival spectrum of the star 51 Peg (<italic>HST</italic> root name O6IH50050) taken in approximately the same wavelength range, only a day prior to the observations described here. By fitting this PSF to the data in <xref ref-type="fig" rid="fig001">Fig. 1</xref>, we are able to define suitable extraction bands for each one of the components. These bands are listed in <xref ref-type="fig" rid="tbl002">Table 2</xref>, with positions relative to the centre of component A. Estimates of the cross-contamination from the other quasar components and the fraction of the flux missed are also given in the table (assuming the model PSF derived from the 51 Peg observation). The worst case is clearly image C, where the extracted spectrum has a total of ∼10 per cent contamination from components A and B, and is missing ∼30 per cent of the flux.</p>
<fig id="tbl002" position="anchor">
<label>2</label>
<caption><p>Summary of data reduction.</p></caption>
<graphic mimetype="image" xlink:href="334-1-L7-tbl002.tif"></graphic>
</fig>
<p>HeAr arc-lamp spectra were also extracted from the arc-lamp spectral image from identical regions as the object spectra. These arc-lamp spectra were used to wavelength calibrate the observed QSO spectra which were then rebinned on to the interval λ= 5965Å to λ= 6534Å with linear wavelength steps. Finally, the five spectral observations of the three QSO images were combined using a median-combining algorithm. <xref ref-type="fig" rid="fig002">Fig. 2</xref> displays the three spectra obtained in this manner.</p>
<fig id="fig002" position="anchor">
<label>2</label>
<caption>
<p>The spectra of the three QSO images A, B and C (from top to bottom). While differences in the individual spectra are apparent, the lower panel confirms that image C is of the quasar. As well as the prominent emission line structure due to Ly<sub>α/</sub>N <sub>v</sub>, strong Mg <sub>ii</sub>λλ 2796, 2803 absorption at <italic>z</italic>= 1.18 due to a foreground galaxy is labelled. One striking feature is the presence of Mg <sub>ii</sub> absorption at <italic>z</italic>= 1.21 (∼6190Å), also labelled, which, while being strong in image A, is weaker in C and non-existent in image B, suggesting a non-uniform covering factor across the images (<xref ref-type="bibr" rid="bib17">Petitjean et al. 2000</xref>).</p>
</caption>
<graphic mimetype="image" xlink:href="334-1-L7-fig002.gif"></graphic>
</fig>
</sec>
</sec>
<sec id="ss3">
<title>3 DISCUSSION</title>
<sec id="ss3-1">
<title>3.1 The nature of component C</title>
<p>A cursory examination of the individual spectra of the three images presented in <xref ref-type="fig" rid="fig002">Fig. 2</xref> clearly reveals that each is of the quasar source, and, therefore, image C represents a third image of the quasar and is not the lensing galaxy. This confirms earlier interpretations of the available photometric data (<xref ref-type="bibr" rid="bib7">Ibata et al. 1999</xref>; <xref ref-type="bibr" rid="bib3">Egami et al. 2000</xref>; <xref ref-type="bibr" rid="bib14">Munoz et al. 2001</xref>).</p>
</sec>
<sec id="ss3-2">
<title>3.2 Spectral differences</title>
<p>A more detailed examination of the three spectra in <xref ref-type="fig" rid="fig002">Fig. 2</xref>, however, also reveals that they are not identical. Even accounting for the strong Mg <sub>ii</sub> doublet lines near 6100Å (at <italic>z</italic><sub>abs</sub>= 1.181), probably due to the presence of the lensing galaxy, and for the Lyα and N <sub>v</sub> BAL features below ∼6040Å, it is evident that the equivalent width of the Lyα+ N <sub>v</sub> emission line blend near 6050Å is different in each of the three images. Relative to the continuum, the emission lines are strongest in image C and weakest in B.</p>
<p>These differences are summarized in <xref ref-type="fig" rid="tbl003">Table 3</xref> (where we have corrected for the missing flux in the spectrum extraction procedure). For the continuum level we adopted the mean observed flux in the wavelength interval 6250–6350Å which, at <italic>z</italic><sub>em</sub>= 3.911, corresponds to rest wavelengths 1273–1293Å; this is a region free of prominent emission lines and provides a good measure of the QSO continuum (<xref ref-type="bibr" rid="bib6">Francis et al. 1991</xref>). The peak emission line flux was measured between 6040 and 6060Å (1230–1234Å in the rest frame of APM08279+5255) after subtracting the underlying continuum. It can be seen from <xref ref-type="fig" rid="tbl003">Table 3</xref> that the contrast of image C relative to A and B is more pronounced in the continuum than in the emission lines; when viewed in the emission line light, images B and C are of comparable brightness.</p>
<fig id="tbl003" position="anchor">
<label>3</label>
<caption><p>Continuum to emission line flux ratios.</p></caption>
<graphic mimetype="image" xlink:href="334-1-L7-tbl003.tif"></graphic>
</fig>
<p>Such spectral differences are a natural consequence of differential microlensing effects, with the small continuum emitting source being more severely influenced by the action of microlensing than the larger line emitting region (e.g. <xref ref-type="bibr" rid="bib18">Saust 1994</xref>). In fact, it is generally thought that the scale of the BAL region is sufficient for it to be immune from significant microlensing influences (<xref ref-type="bibr" rid="bib16">Nemiroff 1988</xref>; <xref ref-type="bibr" rid="bib19">Schneider & Wambsganss 1990</xref>), and hence it reflects the magnification due to the macrolens. While unresolved photometric monitoring of APM08279+5255 reveals that this system has exhibited pronounced variability over several tenths of a magnitude (<xref ref-type="bibr" rid="bib12">Lewis, Robb & Ibata 1999</xref>, see also the continuing monitoring program at the Wise Observatory at ), the spectroscopic evidence presented here points to the variation being potentially due to gravitational microlensing.</p>
<p>Hence, we conclude that the macrolensing magnifications of images B and C, based on the emission lines, are comparable, and it is these that should be used in gravitational lens modelling of this system, rather than the continuum flux. We note that a similar conclusion was reached by <xref ref-type="bibr" rid="bib13">Lewis et al. (2002)</xref> who, based on extended CO emission in this system, demonstrated that the likely lens is a highly flattened object, such as an edge-on spiral. While their model predicted that these images should be ∼75 per cent the brightness of image A, they do concede that currently there are not enough constraints to uniquely tie down a model. The magnifications presented in this paper, therefore, will aid in the modelling of this unique ternary gravitational lens system. It is important to note, however, that dust in the lensing galaxy may result in extinction of some of the quasars flux, especially image C which may be viewed through the disc of a spiral system, and the values presented in <xref ref-type="fig" rid="tbl003">Table 3</xref> may not truly reflect the magnifications of the macromodel. While dust can extinct the quasar images, it cannot be responsible for the differing line-to-continuum ratios observed in the STIS spectra, and hence the conclusion on gravitational microlensing in this system is robust.</p>
<p>It is also interesting to note that, compared to the emission line flux, while the continuum in image B appears to be enhanced, the continuum in image C appears to be depressed. Such a situation occurs during a microlensing demagnification and is seen dramatically in image D of the quadruple lens Q2237+0305 (<xref ref-type="bibr" rid="bib11">Lewis et al. 1998b)</xref>. With such a delineation in microlensing effects, an estimate of the size of the emission regions can be made. Regions significantly smaller than the gravitational microlensing scalelength, the Einstein radius, (i.e. the continuum emitting region) can be significantly influenced during microlensing, while regions significantly larger (e.g. the broad emission line region) are not. The source plane Einstein radius, η, is given by<disp-formula id="eq001">
<label>1</label>
<graphic mimetype="image" xlink:href="334-1-L7-eq001.tif"></graphic>
</disp-formula>
where <italic>D</italic><sub><italic>ij</italic></sub> are the angular diameter distances between an observer (o), lens (l) and source (s). For APM08279+5255, <inline-graphic mimetype="image" xlink:href="334-1-L7-ieq001.tif"></inline-graphic> for an Ω<sub>o</sub>= 1 cosmology, where <italic>M</italic> is the typical microlensing mass. Of course, confirmation of the gravitational lens nature of these spectral features, and hence the applicability of this delineation scalelength, requires further time resolved spectroscopy. While spatially resolved spectroscopy, as presented in this paper, would be ideal, variability in the equivalent widths of the emission lines should be apparent in unresolved ground-based spectra.</p>
</sec>
<sec id="ss3-3">
<title>3.3 Where is the lensing galaxy?</title>
<p>The spectra were examined for a signature of the lensing galaxy. The models of <xref ref-type="bibr" rid="bib7">Ibata et al. (1999)</xref>, <xref ref-type="bibr" rid="bib3">Egami et al. (2000)</xref> and <xref ref-type="bibr" rid="bib14">Munoz et al. (2001)</xref> all place the lensing galaxy in the close vicinity of the quasar images, although to account for the relative image brightnesses, this lensing galaxy possesses an implausibly large core. Using a flattened potential and explaining the relative image brightnesses as due to the influence of a ‘naked cusp’, <xref ref-type="bibr" rid="bib13">Lewis et al. (2002)</xref> find that the lens galaxy is offset by ∼0.5 arcsec from the quasar images.</p>
<p>The data were examined for evidence of the lensing galaxy. Unfortunately, it was found that it is not possible to place any stringent constraints on the lensing galaxy from these observations. The reason for this is that the PSF model we employed does not give an accurate representation of our observations (the spatial profile of the 51 Peg spectra is not as strongly asymmetric as the profile shown in <xref ref-type="fig" rid="fig001">Fig. 1</xref>), and it was not possible to subtract off the bright quasar images to better than ∼2 per cent using that model PSF. By considering the residual luminosity in dark troughs in a Keck HIRES spectrum of this system (<xref ref-type="bibr" rid="bib4">Ellison et al. 1999a</xref>,<xref ref-type="bibr" rid="bib5">b</xref>), <xref ref-type="bibr" rid="bib7">Ibata et al. (1999)</xref> showed that the lensing galaxy must be at least 7 mag fainter than image A, so the present constraint contributes no additional useful information.</p>
</sec>
</sec>
<sec id="ss4">
<title>4 CONCLUSIONS</title>
<p>In this paper we have presented spatially resolved spectra of the gravitationally lensed BAL quasar APM08279+5255 obtained with STIS on the <italic>HST</italic>. They clearly show that each of the three point-like sources are images of the background quasar, confirming that APM08279+5255 represent the first truly odd-image lens system.</p>
<p>An examination of the spectra reveals significant differences in the equivalent widths of the Lyα+ N V emission feature between the images. Such differences are naturally explained by the differential magnification influence of gravitational microlensing, which affects the small continuum source but not the larger broad emission line region of the QSO. While further spectroscopic monitoring is necessary to confirm this microlensing hypothesis, unresolved ground-based observations should be adequate for this purpose (as they will still show variations in the equivalent widths of the emission lines).</p>
<p>Finally, the spectra where examined for evidence of the lensing galaxy. While the <italic>HST</italic> resolution allowed us to extract the spectra of individual quasar images, uncertainties in the point spread function of the instrument limited the accuracy of the subtraction to ∼2 per cent. Available imaging and spectroscopy data show that the lensing galaxy must be significantly fainter than 2 per cent of the QSO images, so that we cannot detect it in the present set of observations.</p>
</sec>
</body>
<back>
<ref-list>
<title>REFERENCES</title>
<ref id="bib1">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Bartelmann</surname><given-names>M.</given-names></name>
<name><surname>Loeb</surname><given-names>A.</given-names></name>
</person-group>, <year>1998</year>, <source>ApJ</source>, <volume>503</volume>, <fpage>48</fpage>
</citation>
</ref>
<ref id="bib2">
<citation citation-type="other">
<person-group person-group-type="author"><name><surname>Burke</surname><given-names>W. L.</given-names></name></person-group>, <year>1981</year>, <source>ApJ</source>, <volume>244</volume>, <fpage>L1</fpage>
</citation>
</ref>
<ref id="bib3">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Egami</surname><given-names>E.</given-names></name>
<name><surname>Neugebauer</surname><given-names>G.</given-names></name>
<name><surname>Soifer</surname><given-names>B. T.</given-names></name>
<name><surname>Matthews</surname><given-names>K.</given-names></name>
<name><surname>Ressler</surname><given-names>M.</given-names></name>
<name><surname>Becklin</surname><given-names>E. E.</given-names></name>
<name><surname>Murphy</surname><given-names>T. W.</given-names></name>
<name><surname>Dale</surname><given-names>D. A.</given-names></name>
</person-group>, <year>2000</year>, <source>ApJ</source>, <volume>535</volume>, <fpage>561</fpage>
</citation>
</ref>
<ref id="bib4">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Ellison</surname><given-names>S. L.</given-names></name>
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Pettini</surname><given-names>M.</given-names></name>
<name><surname>Sargent</surname><given-names>W. L. W.</given-names></name>
<name><surname>Chaffee</surname><given-names>F. H.</given-names></name>
<name><surname>Foltz</surname><given-names>C. B.</given-names></name>
<name><surname>Rauch</surname><given-names>M.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
</person-group>, <year>1999</year>a, <source>PASP</source>, <volume>111</volume>, <fpage>946</fpage>
</citation>
</ref>
<ref id="bib5">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Ellison</surname><given-names>S. L.</given-names></name>
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Pettini</surname><given-names>M.</given-names></name>
<name><surname>Chaffee</surname><given-names>F. H.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
</person-group>, <year>1999</year>b, <source>ApJ</source>, <volume>520</volume>, <fpage>456</fpage>
</citation>
</ref>
<ref id="bib6">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Francis</surname><given-names>P. J.</given-names></name>
<name><surname>Hewett</surname><given-names>P. C.</given-names></name>
<name><surname>Foltz</surname><given-names>C. B.</given-names></name>
<name><surname>Chaffee</surname><given-names>F. H.</given-names></name>
<name><surname>Weymann</surname><given-names>R. J.</given-names></name>
<name><surname>Morris</surname><given-names>S. L.</given-names></name>
</person-group>, <year>1991</year>, <source>ApJ</source>, <volume>373</volume>, <fpage>465</fpage>
</citation>
</ref>
<ref id="bib7">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Ibata</surname><given-names>R. A.</given-names></name>
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
<name><surname>Lehár</surname><given-names>J.</given-names></name>
<name><surname>Totten</surname><given-names>E. J.</given-names></name>
</person-group>, <year>1999</year>, <source>AJ</source>, <volume>118</volume>, <fpage>1922</fpage>
</citation>
</ref>
<ref id="bib8">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
<name><surname>Ibata</surname><given-names>R. A.</given-names></name>
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Totten</surname><given-names>E. J.</given-names></name>
</person-group>, <year>1998</year>, <source>ApJ</source>, <volume>505</volume>, <fpage>529</fpage>
</citation>
</ref>
<ref id="bib9">
<citation citation-type="other">
<person-group person-group-type="author"><name><surname>Ledoux</surname><given-names>C.</given-names></name>
<name><surname>Theodore</surname><given-names>B.</given-names></name>
<name><surname>Petitjean</surname><given-names>P.</given-names></name>
<name><surname>Bremer</surname><given-names>M. N.</given-names></name>
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Ibata</surname><given-names>R. A.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
<name><surname>Totten</surname><given-names>E. J.</given-names></name></person-group>, <year>1998</year>, <source>A&A</source>, <volume>339</volume>, <fpage>L77</fpage>
</citation>
</ref>
<ref id="bib10">
<citation citation-type="other">
<person-group person-group-type="author"><name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Chapman</surname><given-names>S. C.</given-names></name>
<name><surname>Ibata</surname><given-names>R. A.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
<name><surname>Totten</surname><given-names>E. J.</given-names></name></person-group>, <year>1998</year>, <source>ApJ</source>, <volume>550</volume>, <fpage>L1</fpage>
</citation>
</ref>
<ref id="bib11">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Irwin</surname><given-names>M. J.</given-names></name>
<name><surname>Hewett</surname><given-names>P. C.</given-names></name>
<name><surname>Foltz</surname><given-names>C. B.</given-names></name>
</person-group>, <year>1998</year>b, <source>MNRAS</source>, <volume>295</volume>, <fpage>573</fpage>
</citation>
</ref>
<ref id="bib12">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Robb</surname><given-names>R. M.</given-names></name>
<name><surname>Ibata</surname><given-names>R. A.</given-names></name>
</person-group>, <year>1999</year>, <source>PASP</source>, <volume>111</volume>, <fpage>1503</fpage>
</citation>
</ref>
<ref id="bib13">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Lewis</surname><given-names>G. F.</given-names></name>
<name><surname>Carilli</surname><given-names>C.</given-names></name>
<name><surname>Papadopoulos</surname><given-names>P.</given-names></name>
<name><surname>Ivison</surname><given-names>R. J.</given-names></name>
</person-group>, <year>2002</year>, <source>MNRAS</source>, <volume>330</volume>, <fpage>L15</fpage>
</citation>
</ref>
<ref id="bib14">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Munoz</surname><given-names>J. A.</given-names></name>
<name><surname>Kochanek</surname><given-names>C. S.</given-names></name>
<name><surname>Keeton</surname><given-names>C. R.</given-names></name>
</person-group>, <year>2001</year>, <source>ApJ</source>, <volume>558</volume>, <fpage>657</fpage>
</citation>
</ref>
<ref id="bib15">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Narasimha</surname><given-names>D.</given-names></name>
<name><surname>Subramanian</surname><given-names>K.</given-names></name>
<name><surname>Chitre</surname><given-names>S. M.</given-names></name>
</person-group>, <year>1986</year>, <source>Nat</source>, <volume>321</volume>, <fpage>45</fpage>
</citation>
</ref>
<ref id="bib16">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Nemiroff</surname><given-names>R. J.</given-names></name>
</person-group>, <year>1988</year>, <source>ApJ</source>, <volume>335</volume>, <fpage>593</fpage>
</citation>
</ref>
<ref id="bib17">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Petitjean</surname><given-names>P.</given-names></name>
<name><surname>Aracil</surname><given-names>B.</given-names></name>
<name><surname>Srianand</surname><given-names>R.</given-names></name>
<name><surname>Ibata</surname><given-names>R.</given-names></name>
</person-group>, <year>2000</year>, <source>A&A</source>, <volume>359</volume>, <fpage>457</fpage>
</citation>
</ref>
<ref id="bib18">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Saust</surname><given-names>A. B.</given-names></name>
</person-group>, <year>1994</year>, <source>A&AS</source>, <volume>103</volume>, <fpage>33</fpage>
</citation>
</ref>
<ref id="bib19">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Schneider</surname><given-names>P.</given-names></name>
<name><surname>Wambsganss</surname><given-names>J.</given-names></name>
</person-group>, <year>1990</year>, <source>A&A</source>, <volume>237</volume>, <fpage>42</fpage>
</citation>
</ref>
<ref id="bib20">
<citation citation-type="journal">
<person-group person-group-type="author">
<name><surname>Srianand</surname><given-names>R.</given-names></name>
<name><surname>Petitjean</surname><given-names>P.</given-names></name>
</person-group>, <year>2000</year>, <source>A&A</source>, <volume>357</volume>, <fpage>414</fpage>
</citation>
</ref>
</ref-list>
</back>
</article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title></titleInfo><titleInfo type="alternative" contentType="CDATA"><title>Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing</title></titleInfo><name type="personal" displayLabel="corresp"><namePart type="given">Geraint F.</namePart><namePart type="family">Lewis</namePart><affiliation>Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Rodrigo A.</namePart><namePart type="family">Ibata</namePart><affiliation>Observatoire de Strabourg, 11, rue de l'Universite, F-67000, Strasbourg, France</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Sara L.</namePart><namePart type="family">Ellison</namePart><affiliation>European Southern Observatory, Casilla 19001, Santiago 19, Chile</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Bastien</namePart><namePart type="family">Aracil</namePart><affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Patrick</namePart><namePart type="family">Petitjean</namePart><affiliation>Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, F-75014 Paris, France</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Max</namePart><namePart type="family">Pettini</namePart><affiliation>Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Raghunathan</namePart><namePart type="family">Srianand</namePart><affiliation>IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007, India</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</affiliation><affiliation>E-mail: gfl@aaoepp.aao.gov.au</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><dateIssued encoding="w3cdtf">2002-07-21</dateIssued><copyrightDate encoding="w3cdtf">2002</copyrightDate></originInfo><abstract>While gravitationally lensed quasars are expected to display an odd number of images, invariably systems are observed with an even number of quasars. For this, lensing galaxies must have very small core radii; this provides strong demagnification of one of the images. High-resolution imaging of the gravitationally lensed broad absorption line (BAL) quasar, APM08279+5255, reveals three point-like images. As these images possess similar colours, it has been suggested that each represents a lensed image. Here, spatially resolved spectra of the individual components, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), are presented, clearly revealing that each is an image of the quasar. This confirms that APM08279+5255 represents the first example of an odd-image gravitationally lensed system. The implications for the properties of the lensing galaxy are discussed. It is also found that the individual images possess spectral differences indicative of the influence of gravitational microlensing in this system.</abstract><subject><genre>Key words</genre><topic>gravitational lensing</topic><topic>quasars: individual: APM08279+5255</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>2002</date><detail type="volume"><caption>vol.</caption><number>334</number></detail><detail type="issue"><caption>no.</caption><number>1</number></detail><extent unit="pages"><start>L7</start><end>L10</end></extent></part></relatedItem><identifier type="istex">0644AA2C1BDB1911D5BF828A66A06779528BEA1C</identifier><identifier type="DOI">10.1046/j.1365-8711.2002.05700.x</identifier><accessCondition type="use and reproduction" contentType="copyright">© 2002 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>© 2002 RAS</recordOrigin></recordInfo></mods><json:item><extension>json</extension><original>false</original><mimetype>application/json</mimetype><uri>https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/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/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/annexes/jpeg</uri></json:item><json:item><extension>gif</extension><original>true</original><mimetype>image/gif</mimetype><uri>https://api.istex.fr/document/0644AA2C1BDB1911D5BF828A66A06779528BEA1C/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 000115 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Istex/Corpus/biblio.hfd -nk 000115 | 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:0644AA2C1BDB1911D5BF828A66A06779528BEA1C
|texte= Spatially resolved STIS spectra of the gravitationally lensed broad absorption line quasar APM08279+5255: the nature of component C and evidence for microlensing
}}
| This area was generated with Dilib version V0.6.33. |  |