PAndAS' cubs: discovery of two new dwarf galaxies in the surroundings of the Andromeda and Triangulum galaxies

Abstract

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 (PAndAS), 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_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_V=-6.5+/-0.8) and lies a lot closer in projection to M33 than it does to M31 (42 vs. 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.

10 pages, 6 figures, accepted for publication in ApJ; v2: minor typographical corrections

References in corpus (16)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The Dartmouth Stellar Evolution Database
• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• The remnants of galaxy formation from a panoramic survey of the region around M31
• The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy formation in action
• The Luminosity Function of the Milky Way Satellites
• Discovery and analysis of three faint dwarf galaxies and a globular cluster in the outer halo of the Andromeda galaxy
• The Cold Dark Matter Halos of Local Group Dwarf Spheroidals
• The Invisibles: A Detection Algorithm to Trace the Faintest Milky Way Satellites
• A deep kinematic survey of planetary nebulae in the Andromeda Galaxy using the Planetary Nebula Spectrograph
• A trio of new Local Group galaxies with extreme properties
• Satellites of Simulated Galaxies: survival, merging, and their relation to the dark and stellar halos
• The stellar halo and outer disk of M33
• Andromeda XVII: A New Low Luminosity Satellite of M31
• A Revised LCDM Mass Model For The Andromeda Galaxy
• Strangers in the night: Discovery of a dwarf spheroidal galaxy on its first Local Group infall

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