DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY

T. S. Li, E. Balbinot, N. Mondrik, J. L. Marshall, B. Yanny, K. Bechtol, A. Drlica-Wagner, D. Oscar, B. Santiago, J. D. Simon, A. K. Vivas, A. R. Walker, M. Y. Wang, T. M.C. Abbott, F. B. Abdalla, A. Benoit-Lévy, G. M. Bernstein, E. Bertin, D. Brooks, D. L. BurkeA. Carnero Rosell, M. Carrasco Kind, J. Carretero, L. N.Da Costa, D. L. Depoy, S. Desai, H. T. Diehl, P. Doel, J. Estrada, D. A. Finley, B. Flaugher, J. Frieman, D. Gruen, R. A. Gruendl, G. Gutierrez, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, O. Lahav, M. A.G. Maia, M. March, P. Martini, R. Ogando, A. A. Plazas, K. Reil, A. K. Romer, A. Roodman, E. Sanchez, V. Scarpine, M. Schubnell, I. Sevilla-Noarbe, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E.C. Swanson, G. Tarle, D. Tucker, Y. Zhang

    Research output: Contribution to journalReview articleResearchpeer-review

    22 Citations (Scopus)

    Abstract

    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° and b ∼ -60° and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9s. 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.
    Original languageEnglish
    Article number135
    JournalAstrophysical Journal
    Volume817
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 2016

    Keywords

    • galaxy: formation
    • galaxy: halo
    • galaxy: structure
    • local group

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