PAndAS' PROGENY: EXTENDING THE M31 DWARF GALAXY CABAL
- Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
- NRC Herzberg Institute for Astrophysics, 5071 West Saanich Road, Victoria, British Columbia, V9E 2E7 (Canada)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)
- Observatoire de Strasbourg, 11, rue de l'Universite, F-67000, Strasbourg (France)
- Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
We present the discovery of five new dwarf galaxies, Andromeda XXIII-XXVII, located in the outer halo of M31. These galaxies were discovered during the second year of data from the Pan-Andromeda Archaeological Survey (PAndAS), a photometric survey of the M31/M33 subgroup conducted with the MegaPrime/MegaCam wide-field camera on the Canada-France-Hawaii Telescope. The current PAndAS survey now provides an almost complete panoramic view of the M31 halo out to an average projected radius of {approx}150 kpc. Here we present for the first time the metal-poor stellar density map for this whole region, not only as an illustration of the discovery space for satellite galaxies, but also as a birds-eye view of the ongoing assembly process of an L{sub *} disk galaxy. Four of the newly discovered satellites appear as well-defined spatial overdensities of stars lying on the expected locus of metal-poor (-2.5 < [Fe/H] < -1.3) red giant branch stars at the distance of M31. The fifth overdensity, And XXVII, is embedded in an extensive stream of such stars and is possibly the remnant of a strong tidal disruption event. Based on distance estimates from horizontal branch magnitudes, all five have metallicities typical of dwarf spheroidal galaxies ranging from [Fe/H] =-1.7 {+-} 0.2 to [Fe/H] =-1.9 {+-} 0.2 and absolute magnitudes ranging from M{sub V} = -7.1 {+-} 0.5 to M{sub V} = -10.2 {+-} 0.5. These five additional satellites bring the number of dwarf spheroidal galaxies in this region to 25 and continue the trend whereby the brighter dwarf spheroidal satellites of M31 generally have much larger half-light radii than their Milky Way counterparts. With an extended sample of M31 satellite galaxies, we also revisit the spatial distribution of this population and in particular we find that, within the current projected limits of the PAndAS survey, the surface density of satellites is essentially constant out to 150 kpc. This corresponds to a radial density distribution of satellites varying as r{sup -1}, a result seemingly in conflict with the predictions of cosmological simulations.
- OSTI ID:
- 21576882
- Journal Information:
- Astrophysical Journal, Vol. 732, Issue 2; Other Information: DOI: 10.1088/0004-637X/732/2/76; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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