HYDRA II: A FAINT AND COMPACT MILKY WAY DWARF GALAXY FOUND IN THE SURVEY OF THE MAGELLANIC STELLAR HISTORY

Nicolas F. Martin, David L. Nidever, Gurtina Besla, Knut Olsen, Alistair R. Walker, A. Katherina Vivas, Robert A. Gruendl, Catherine C. Kaleida, Ricardo R. Muñoz, Robert D. Blum, Abhijit Saha, Blair C. Conn, Eric F. Bell, You Hua Chu, Maria Rosa L. Cioni, Thomas J.L. De Boer, Carme Gallart, Shoko Jin, Andrea Kunder, Steven R. MajewskiDavid Martinez-Delgado, Antonela Monachesi, Matteo Monelli, Lara Monteagudo, Noelia E.D. Noël, Edward W. Olszewski, Guy S. Stringfellow, Roeland P. Van Der Marel, Dennis Zaritsky

Research output: Contribution to journalArticlepeer-review

154 Scopus citations

Abstract

We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact (rh = 68 ± 11 pc) and faint (MV = -4.8 ± 0.3), but well within the realm of dwarf galaxies. The stellar distribution of Hydra II in the color-magnitude diagram is well-described by a metal-poor ([Fe/H] = -2.2) and old (13 Gyr) isochrone and shows a distinct blue horizontal branch, some possible red clump stars, and faint stars that are suggestive of blue stragglers. At a heliocentric distance of 134 ± 10 kpc, Hydra II is located in a region of the Galactic halo that models have suggested may host material from the leading arm of the Magellanic Stream. A comparison with N-body simulations hints that the new dwarf galaxy could be or could have been a satellite of the Magellanic Clouds.

Original languageEnglish (US)
Article numberL5
JournalAstrophysical Journal Letters
Volume804
Issue number1
DOIs
StatePublished - May 1 2015

Keywords

  • Local Group
  • Magellanic Clouds
  • galaxies: individual (Hydra II)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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