Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
Creators: name: The DES Collaboration
name: Bechtol, K.
name: Drlica-Wagner, A.
name: Balbinot, E.
name: Pieres, A.
name: Simon, J. D.
name: Yanny, B.
name: Santiago, B.
name: Wechsler, R. H.
name: Frieman, J.
name: Walker, A. R.
name: Williams, P.
name: Rozo, E.
name: Rykoff, E. S.
name: Queiroz, A.
name: Luque, E.
name: Benoit-Levy, A.
name: Tucker, D.
name: Sevilla, I.
name: Gruendl, R. A.
name: da Costa, L. N.
name: Neto, A. Fausti
name: Maia, M. A. G.
name: Abbott, T.
name: Allam, S.
name: Armstrong, R.
name: Bauer, A. H.
name: Bernstein, G. M.
name: Bernstein, R. A.
name: Bertin, E.
name: Brooks, D.
name: Buckley-Geer, E.
name: Burke, D. L.
name: Rosell, A. Carnero
name: Castander, F. J.
name: Covarrubias, R.
name: D'Andrea, C. B.
name: DePoy, D. L.
name: Desai, S.
name: Diehl, H. T.
name: Eifler, T. F.
name: Estrada, J.
name: Evrard, A. E.
name: Fernandez, E.
name: Finley, D. A.
name: Flaugher, B.
name: Gaztanaga, E.
name: Gerdes, D.
name: Girardi, L.
name: Gladders, M.
name: Gruen, D.
name: Gutierrez, G.
name: Hao, J.
name: Honscheid, K.
name: Jain, B.
name: James, D.
name: Kent, S.
name: Kron, R.
name: Kuehn, K.
name: Kuropatkin, N.
name: Lahav, O.
name: Li, T. S.
name: Lin, H.
name: Makler, M.
name: March, M.
name: Marshall, J.
name: Martini, P.
name: Merritt, K. W.
name: Miller, C.
name: Miquel, R.
name: Mohr, J.
name: Neilsen, E.
name: Nichol, R.
name: Nord, B.
name: Ogando, R.
name: Peoples, J.
name: Petravick, D.
name: Plazas, A. A.
name: Romer, A. K.
name: Roodman, A.
name: Sako, M.
name: Sanchez, E.
name: Scarpine, V.
name: Schubnell, M.
name: Smith, R. C.
name: Soares-Santos, M.
name: Sobreira, F.
name: Suchyta, E.
name: Swanson, M. E. C.
name: Tarle, G.
name: Thaler, J.
name: Thomas, D.
name: Wester, W.
name: Zuntz, J.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the discovery of eight new Milky Way companions in ~1,800 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 (M_V from -2.2 mag to -7.4 mag), physical sizes (10 pc to 170 pc), and heliocentric distances (30 kpc to 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.
description: 33 pages, 12 figures, 3 tables. Accepted for publication in ApJ. Readers may be interested in the concurrent work by Koposov, Belokurov, Torrealba, &amp; Evans (http://arxiv.org/abs/1503.02079). Indirect dark matter search results are presented in Drlica-Wagner, Albert, Bechtol, Wood, Strigari, et al. (The LAT and DES Collaborations, http://arxiv.org/abs/1503.02632)