Discovery of a stellar overdensity in Eridanus-Phoenix in the Dark Energy Survey

Li, T S, Balbinot, E, Mondrik, N, Marshall, J L, Yanny, B, Bechtol, K, Drlica-Wagner, A, Oscar, D, Santiago, B, Simon, J D, Vivas, A K, Walker, A R, Wang, M Y, Abbott, T M C, Abdalla, F B, Benoit-Lévy, A, Bernstein, G M, Bertin, E, Brooks, D, Burke, D L, Carnero Rosell, A, Carrasco Kind, M, Carretero, J, da Costa, L N, DePoy, D L, Desai, S, Diehl, H T, Doel, P, Estrada, J, Finley, D A, Flaugher, B, Frieman, J, Gruen, D, Gruendl, R A, Gutierrez, G, Honscheid, K, James, D J, Kuehn, K, Kuropatkin, N, Lahav, O, Maia, M A G, March, M, Martini, P, Ogando, R, Plazas, A A, Reil, K, Romer, A K, Roodman, A, Sanchez, E, Scarpine, V, Schubnell, M, Sevilla-Noarbe, I, Smith, R C, Soares-Santos, M, Sobreira, F, Suchyta, E, Swanson, M E C, Tarle, G, Tucker, D and Zhang, Y (2016) Discovery of a stellar overdensity in Eridanus-Phoenix in the Dark Energy Survey. The Astrophysical Journal, 817 (2). p. 135. ISSN 1538-4357

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We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l˜ 285^\circ and b˜ -60^\circ and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9sigma . The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d˜ 16 {{kpc}}. The extent of EriPhe in projection is therefore at least ˜4 kpc by ˜3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ˜120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

Item Type: Article
Keywords: Galaxy: formation, Galaxy: halo, Galaxy: structure, Local group
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Richard Chambers
Date Deposited: 24 Jun 2016 08:27
Last Modified: 31 Mar 2017 12:03

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Project NameSussex Project NumberFunderFunder Ref
Astrophysics and Cosmology - Sussex Consolidated GrantG1291STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/L000652/1