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Eight New Milky Way Companions Discovered in First-year Dark Energy Survey Data

Abstract : We report the discovery of eight new Milky Way companions in ∼ 1800 {{deg}}2 of optical imaging data collected during the first year of the Dark Energy Survey (DES). Each system is identified as a statistically significant over-density of individual stars consistent with the expected isochrone and luminosity function of an old and metal-poor stellar population. The objects span a wide range of absolute magnitudes (MV from -2.2 to -7.4 {mag}), physical sizes (10-170 {pc}), and heliocentric distances (30-330 {kpc}). Based on the low surface brightnesses, large physical sizes, and/or large Galactocentric distances of these objects, several are likely to be new ultra-faint satellite galaxies of the Milky Way and/or Magellanic Clouds. We introduce a likelihood-based algorithm to search for and characterize stellar over-densities, as well as identify stars with high satellite membership probabilities. We also present completeness estimates for detecting ultra-faint galaxies of varying luminosities, sizes, and heliocentric distances in the first-year DES data.
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Submitted on : Tuesday, April 19, 2022 - 2:42:30 PM
Last modification on : Wednesday, April 20, 2022 - 3:40:08 AM

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K. Bechtol, A. Drlica-Wagner, E. Balbinot, A. Pieres, J. D. Simon, et al.. Eight New Milky Way Companions Discovered in First-year Dark Energy Survey Data. The Astrophysical Journal, 2015, 807, ⟨10.1088/0004-637X/807/1/50⟩. ⟨insu-03644908⟩

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