Hydra II: a faint and compact milky way dwarf galaxy found in the survey of the magellanic stellar history
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Author
Martin, Nicolas F.
Nidever, David L.
Besla, Gurtina
Olsen, Knut
Walker, Alistair R.
Vivas, A. Katherina
Gruendl, Robert A.
Kaleida, Catherine C.
Muñoz, Ricardo R.
Blum, Robert D.
Saha, Abhijit
Conn, Blair C.
Bell, Eric F.
Chu, You Hua
Cioni, M-R.L.
De Boer, Thomas J. L.
Gallart, Carme
Jin, Shoko
Kunder, Andrea
Majewski, Steven R.
Martinez-Delgado, David
Monachesi, Antonela
Monelli, Matteo
Monteagudo, Lara
Noël, Noelia E.D.
Olszewski, Edward W.
Stringfellow, Guy S.
Van Der Marel, Roeland P.
Zaritsky, Dennis
Attention
2299/15966
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 (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.