A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies
Identifieur interne : 001471 ( Istex/Checkpoint ); précédent : 001470; suivant : 001472A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies
Auteurs : N. F. Martin [Allemagne] ; R. A. Ibata [France] ; S. C. Chapman [Canada, Allemagne] ; M. Irwin ; G. F. Lewis [Australie]Source :
- Monthly Notices of the Royal Astronomical Society [ 0035-8711 ] ; 2007-09-01.
Descripteurs français
- Wicri :
- topic : Satellite.
English descriptors
- KwdEn :
- Arcmin, Belokurov, Bottom panel, Brighter dwarf galaxies, Brighter galaxies, Carretta gratton, Central panel, Central surface brightness, Central velocity dispersion, Contaminant, Core radius, Cvni, Dark matter, Dark matter halo, Dark matter haloes, Deimos, Direct link, Dispersion, Doublet, Dwarf, Dwarf galaxies, Dwarf galaxy, Faint dwarf galaxies, Faint satellites, Foreground dwarf stars, Galactic, Galactic contaminants, Galaxy, Giant stars, Globular, Globular cluster, Good agreement, Halo, Heliocentric distance, Hollow circles, Ibata, Irwin, Journal compilation, Lled, Lled circles, Local group, Luminosity, Main sequence, Mass estimates, Mass limit, Matter haloes, Median metallicity, Metallicities, Metallicity, Metallicity distribution, Metallicity spread, Milky, Mnras, More details, Narrow peak, Orphan stream, Other hand, Other satellites, Piatek pryor, Pryor, Radial, Radial velocities, Radial velocity, Radial velocity distribution, Radial velocity peak, Richstone tremaine, Satellite, Sdss, Siegel, Solar units, Spectroscopic, Spectroscopic observations, Spectroscopic survey, Star, Structural parameters, Systemic velocity, Thick line, Tidal, Tidal interaction, Total mass, Umai, Umaii, Ursa, Velocity dispersion, Velocity distribution, Velocity peak, Virial equilibrium, Wil1, Wil1 panel, Willman, Zucker.
- Teeft :
- Arcmin, Belokurov, Bottom panel, Brighter dwarf galaxies, Brighter galaxies, Carretta gratton, Central panel, Central surface brightness, Central velocity dispersion, Contaminant, Core radius, Cvni, Dark matter, Dark matter halo, Dark matter haloes, Deimos, Direct link, Dispersion, Doublet, Dwarf, Dwarf galaxies, Dwarf galaxy, Faint dwarf galaxies, Faint satellites, Foreground dwarf stars, Galactic, Galactic contaminants, Galaxy, Giant stars, Globular, Globular cluster, Good agreement, Halo, Heliocentric distance, Hollow circles, Ibata, Irwin, Journal compilation, Lled, Lled circles, Local group, Luminosity, Main sequence, Mass estimates, Mass limit, Matter haloes, Median metallicity, Metallicities, Metallicity, Metallicity distribution, Metallicity spread, Milky, Mnras, More details, Narrow peak, Orphan stream, Other hand, Other satellites, Piatek pryor, Pryor, Radial, Radial velocities, Radial velocity, Radial velocity distribution, Radial velocity peak, Richstone tremaine, Satellite, Sdss, Siegel, Solar units, Spectroscopic, Spectroscopic observations, Spectroscopic survey, Star, Structural parameters, Systemic velocity, Thick line, Tidal, Tidal interaction, Total mass, Umai, Umaii, Ursa, Velocity dispersion, Velocity distribution, Velocity peak, Virial equilibrium, Wil1, Wil1 panel, Willman, Zucker.
Abstract
We present the results of a spectroscopic survey of the recently discovered faint Milky Way satellites Boötes, Ursa Major I, Ursa Major II and Willman 1 (Wil1). Using the DEep Imaging Multi‐Object Spectrograph mounted on the Keck II telescope, we have obtained samples that contain from ∼15 to ∼85 probable members of these satellites for which we derive radial velocities precise to a few km s−1 down to i∼ 21–22. About half of these stars are observed with a high enough signal‐to‐noise ratio to estimate their metallicity to within ±0.2 dex. The characteristics of all the observed stars are made available, along with those of the Canes Venatici I dwarf galaxy that have been analysed in a companion paper. From this data set, we show that Ursa Major II is the only object that does not show a clear radial velocity peak. However, the measured systemic radial velocity (vr= 115 ± 5 km s−1) is in good agreement with simulations in which this object is the progenitor of the recently discovered Orphan Stream. The three other satellites show velocity dispersions that make them highly dark matter dominated systems (under the usual assumptions of symmetry and virial equilibrium). In particular, we show that despite its small size and faintness, the Wil1 object is not a globular cluster given its metallicity scatter over −2.0 ≲[Fe/H]≲−1.0 and is therefore almost certainly a dwarf galaxy or dwarf galaxy remnant. We measure a radial velocity dispersion of only 4.3+2.3−1.3 km s−1 around a systemic velocity of −12.3 ± 2.3 km s−1 which implies a mass‐to‐light ratio of ∼700 and a total mass of ∼5 × 105 M⊙ for this satellite, making it the least massive satellite galaxy known to date. Such a low mass could mean that the 107 M⊙ limit that had until now never been crossed for Milky Way and Andromeda satellite galaxies may only be an observational limit and that fainter, less massive systems exist within the Local Group. However, more modelling and an extended search for potential extratidal stars are required to rule out the possibility that these systems have not been significantly heated by tidal interaction.
Url:
DOI: 10.1111/j.1365-2966.2007.12055.x
Affiliations:
- Allemagne, Australie, Canada, France
- Bade-Wurtemberg, District de Karlsruhe, Nouvelle-Galles du Sud
- Heidelberg, Sydney
- Université de Sydney
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<term>Carretta gratton</term>
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<term>Core radius</term>
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<term>Dark matter halo</term>
<term>Dark matter haloes</term>
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<term>Dwarf galaxies</term>
<term>Dwarf galaxy</term>
<term>Faint dwarf galaxies</term>
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<term>Pryor</term>
<term>Radial</term>
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<term>Radial velocity distribution</term>
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<term>Satellite</term>
<term>Sdss</term>
<term>Siegel</term>
<term>Solar units</term>
<term>Spectroscopic</term>
<term>Spectroscopic observations</term>
<term>Spectroscopic survey</term>
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<term>Structural parameters</term>
<term>Systemic velocity</term>
<term>Thick line</term>
<term>Tidal</term>
<term>Tidal interaction</term>
<term>Total mass</term>
<term>Umai</term>
<term>Umaii</term>
<term>Ursa</term>
<term>Velocity dispersion</term>
<term>Velocity distribution</term>
<term>Velocity peak</term>
<term>Virial equilibrium</term>
<term>Wil1</term>
<term>Wil1 panel</term>
<term>Willman</term>
<term>Zucker</term>
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<keywords scheme="Teeft" xml:lang="en"><term>Arcmin</term>
<term>Belokurov</term>
<term>Bottom panel</term>
<term>Brighter dwarf galaxies</term>
<term>Brighter galaxies</term>
<term>Carretta gratton</term>
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<term>Central surface brightness</term>
<term>Central velocity dispersion</term>
<term>Contaminant</term>
<term>Core radius</term>
<term>Cvni</term>
<term>Dark matter</term>
<term>Dark matter halo</term>
<term>Dark matter haloes</term>
<term>Deimos</term>
<term>Direct link</term>
<term>Dispersion</term>
<term>Doublet</term>
<term>Dwarf</term>
<term>Dwarf galaxies</term>
<term>Dwarf galaxy</term>
<term>Faint dwarf galaxies</term>
<term>Faint satellites</term>
<term>Foreground dwarf stars</term>
<term>Galactic</term>
<term>Galactic contaminants</term>
<term>Galaxy</term>
<term>Giant stars</term>
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<term>Globular cluster</term>
<term>Good agreement</term>
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<term>Heliocentric distance</term>
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<term>Irwin</term>
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<term>Lled circles</term>
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<term>Luminosity</term>
<term>Main sequence</term>
<term>Mass estimates</term>
<term>Mass limit</term>
<term>Matter haloes</term>
<term>Median metallicity</term>
<term>Metallicities</term>
<term>Metallicity</term>
<term>Metallicity distribution</term>
<term>Metallicity spread</term>
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<term>Mnras</term>
<term>More details</term>
<term>Narrow peak</term>
<term>Orphan stream</term>
<term>Other hand</term>
<term>Other satellites</term>
<term>Piatek pryor</term>
<term>Pryor</term>
<term>Radial</term>
<term>Radial velocities</term>
<term>Radial velocity</term>
<term>Radial velocity distribution</term>
<term>Radial velocity peak</term>
<term>Richstone tremaine</term>
<term>Satellite</term>
<term>Sdss</term>
<term>Siegel</term>
<term>Solar units</term>
<term>Spectroscopic</term>
<term>Spectroscopic observations</term>
<term>Spectroscopic survey</term>
<term>Star</term>
<term>Structural parameters</term>
<term>Systemic velocity</term>
<term>Thick line</term>
<term>Tidal</term>
<term>Tidal interaction</term>
<term>Total mass</term>
<term>Umai</term>
<term>Umaii</term>
<term>Ursa</term>
<term>Velocity dispersion</term>
<term>Velocity distribution</term>
<term>Velocity peak</term>
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<term>Wil1 panel</term>
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<front><div type="abstract" xml:lang="en">We present the results of a spectroscopic survey of the recently discovered faint Milky Way satellites Boötes, Ursa Major I, Ursa Major II and Willman 1 (Wil1). Using the DEep Imaging Multi‐Object Spectrograph mounted on the Keck II telescope, we have obtained samples that contain from ∼15 to ∼85 probable members of these satellites for which we derive radial velocities precise to a few km s−1 down to i∼ 21–22. About half of these stars are observed with a high enough signal‐to‐noise ratio to estimate their metallicity to within ±0.2 dex. The characteristics of all the observed stars are made available, along with those of the Canes Venatici I dwarf galaxy that have been analysed in a companion paper. From this data set, we show that Ursa Major II is the only object that does not show a clear radial velocity peak. However, the measured systemic radial velocity (vr= 115 ± 5 km s−1) is in good agreement with simulations in which this object is the progenitor of the recently discovered Orphan Stream. The three other satellites show velocity dispersions that make them highly dark matter dominated systems (under the usual assumptions of symmetry and virial equilibrium). In particular, we show that despite its small size and faintness, the Wil1 object is not a globular cluster given its metallicity scatter over −2.0 ≲[Fe/H]≲−1.0 and is therefore almost certainly a dwarf galaxy or dwarf galaxy remnant. We measure a radial velocity dispersion of only 4.3+2.3−1.3 km s−1 around a systemic velocity of −12.3 ± 2.3 km s−1 which implies a mass‐to‐light ratio of ∼700 and a total mass of ∼5 × 105 M⊙ for this satellite, making it the least massive satellite galaxy known to date. Such a low mass could mean that the 107 M⊙ limit that had until now never been crossed for Milky Way and Andromeda satellite galaxies may only be an observational limit and that fainter, less massive systems exist within the Local Group. However, more modelling and an extended search for potential extratidal stars are required to rule out the possibility that these systems have not been significantly heated by tidal interaction.</div>
</front>
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<li>Canada</li>
<li>France</li>
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<li>District de Karlsruhe</li>
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<tree><noCountry><name sortKey="Irwin, M" sort="Irwin, M" uniqKey="Irwin M" first="M." last="Irwin">M. Irwin</name>
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<country name="Allemagne"><region name="Bade-Wurtemberg"><name sortKey="Martin, N F" sort="Martin, N F" uniqKey="Martin N" first="N. F." last="Martin">N. F. Martin</name>
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<name sortKey="Chapman, S C" sort="Chapman, S C" uniqKey="Chapman S" first="S. C." last="Chapman">S. C. Chapman</name>
<name sortKey="Martin, N F" sort="Martin, N F" uniqKey="Martin N" first="N. F." last="Martin">N. F. Martin</name>
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<country name="Australie"><region name="Nouvelle-Galles du Sud"><name sortKey="Lewis, G F" sort="Lewis, G F" uniqKey="Lewis G" first="G. F." last="Lewis">G. F. Lewis</name>
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