PAndAS' CUBS: DISCOVERY OF TWO NEW DWARF GALAXIES IN THE SURROUNDINGS OF THE ANDROMEDA AND TRIANGULUM GALAXIES

Journal Article · Sun Nov 01 00:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/705/1/758· OSTI ID:21378342

Martin, Nicolas F ^[1]; McConnachie, Alan W ^[2]; Irwin, Mike; Chapman, Scott ^[3]; Widrow, Lawrence M ^[4]; Ferguson, Annette M. N. ^[5]; Ibata, Rodrigo A ^[6]; Dubinski, John ^[7]; Babul, Arif; Navarro, Julio ^[8]; Fardal, Mark ^[9]; Lewis, Geraint F ^[10]

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1. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
2. NRC Herzberg Institute for Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)
3. Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
4. Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, ON K7L 3N6 (Canada)
5. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)
6. Observatoire de Strasbourg, 11, rue de l'Universite, F-67000, Strasbourg (France)
7. Department of Astronomy and Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
8. Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8W 3P6 (Canada)
9. Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
10. Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = -1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (M{sub V} = -9.9 +- 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (M{sub V} = -6.5 +- 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20.

• OSTI ID: 21378342
• Journal Information: Astrophysical Journal, Vol. 705, Issue 1; Other Information: DOI: 10.1088/0004-637X/705/1/758; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CAMERAS
COLOR
MILKY WAY
SATELLITES
STARS
TELESCOPES
VISIBLE RADIATION
ELECTROMAGNETIC RADIATION
GALAXIES
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS