2015/03/31 by Nicolas F. Martin, David L. Nidever, Gurtina Besla +27 · 155 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Dwarf galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Irregular galaxy #Lernaean Hydra #Milky Way #Satellite #Satellite galaxy #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1088/2041-8205/804/1/l5
published in The Astrophysical Journal Letters 804(1), L5 (IOP Publishing) · 7 pages, 4 figures. Accepted for publication in ApJL. v2: minor corrections, conclusions unchanged
arxiv created 2015/04/02 · openalex publication_date 2015/04/23 · arxiv updated 2015/06/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
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 ( ± 11 pc) and faint ( ± 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 ( ) 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.