University of Hertfordshire

From the same journal

From the same journal


  • 907070

    Accepted author manuscript, 698 KB, PDF document

  • 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
  • M-R.L. Cioni
  • Thomas J. L. De Boer
  • Carme Gallart
  • Shoko Jin
  • Andrea Kunder
  • Steven R. Majewski
  • And 9 others
  • David 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
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Original languageEnglish
Article numberL5
JournalAstrophysical Journal Letters
Early online date23 Apr 2015
Publication statusPublished - 1 May 2015


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 (r_h = 68 ± 11 pc) and faint (M_V = -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.


Date of Acceptance: 31/03/2015


ID: 8608630