Eight ultra-faint galaxy candidates discovered in year two of the dark energy survey

Journal Article · Tue Nov 10 00:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/813/2/109· OSTI ID:22882429

Drlica-Wagner, A.; Yanny, B.; Dodelson, S. ^[1]; Bechtol, K. ^[2]; Rykoff, E. S.; Mao, Y. -Y.; Wechsler, R. H. ^[3]; Luque, E.; Queiroz, A.; Santiago, B.; Pieres, A. ^[4]; Simon, J. D. ^[5]; Balbinot, E.; Neto, A. Fausti; Maia, M. A. G. ^[6]; James, D. J.; Walker, A. R. ^[7]; Li, T. S.; Marshall, J. L.; others, and

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1. Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
2. Wisconsin IceCube Particle Astrophysics Center (WIPAC), Madison, WI 53703 (United States)
3. Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 2450, Stanford University, Stanford, CA 94305 (United States)
4. Instituto de Física, UFRGS, Caixa Postal 15051, Porto Alegre, RS-91501-970 (Brazil)
5. Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
6. Laboratório Interinstitucional de e-Astronomia—LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ-20921-400 (Brazil)
7. Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)

We report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. The new systems are faint (M{sub V} > −4.7 mag) and span a range of physical sizes (17 pc < r{sub 1/2} < 181 pc) and heliocentric distances (25 kpc < D{sub ⊙} < 214 kpc). All of the new systems have central surface brightnesses consistent with known ultra-faint dwarf galaxies (μ ≳ 27.5 mag arcsec{sup −2}). Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known Milky Way satellite galaxies. Most of the candidates are found in the southern part of the DES footprint close to the Magellanic Clouds. We find that the DES data alone exclude (p < 10{sup −3}) a spatially isotropic distribution of Milky Way satellites and that the observed distribution can be well, though not uniquely, described by an association between several of the DES satellites and the Magellanic system. Our model predicts that the full sky may hold ∼100 ultra-faint galaxies with physical properties comparable to the DES satellites and that 20%–30% of these would be spatially associated with the Magellanic Clouds.

• OSTI ID: 22882429
• Journal Information: Astrophysical Journal, Vol. 813, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BRIGHTNESS
DISTANCE
DISTRIBUTION
DWARF STARS
LUMINOSITY
MAGELLANIC CLOUDS
MILKY WAY
NONLUMINOUS MATTER
SURFACES