EVIDENCE THAT HYDRA I IS A TIDALLY DISRUPTING MILKY WAY DWARF GALAXY

被引：5

作者：

Hargis, Jonathan R. ^{[1
]}

Kimmig, Brian ^{[1
]}

Willman, Beth ^{[1
,2
,3
]}

Caldwell, Nelson ^{[4
]}

Walker, Matthew G. ^{[5
]}

Strader, Jay ^{[6
]}

Sand, David J. ^{[7
]}

Grillmair, Carl J. ^{[8
]}

Yoon, Joo Heon ^{[9
]}

机构：

[1] Haverford Coll, Dept Astron, 370 Lancaster Ave, Haverford, PA 19041 USA

[2] LSST, 933 North Cherry Ave, Tucson, AZ 85721 USA

[3] Univ Arizona, Steward Observ, 933 North Cherry Ave, Tucson, AZ 85721 USA

[4] Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA

[5] Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA

[6] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA

[7] Texas Tech Univ, Dept Phys, Box 41051, Lubbock, TX 79409 USA

[8] Spitzer Sci Ctr, 1200 E Calif Blvd, Pasadena, CA 91125 USA

[9] Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA

来源：

ASTROPHYSICAL JOURNAL | 2016年 / 818卷 / 01期

基金：

美国国家科学基金会;

关键词：

galaxies: dwarf; Galaxy: halo; Galaxy: structure; EXPLORING HALO SUBSTRUCTURE; GLOBULAR-CLUSTERS; MAGELLANIC-CLOUD; ABUNDANCE RATIOS; RADIAL-VELOCITY; STELLAR SPECTRA; GALACTIC HALO; STAR-CLUSTERS; METALLICITY; SEGUE;

D O I：

10.3847/0004-637X/818/1/39

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The Eastern Banded Structure (EBS) and Hydra. I halo overdensities are very nearby (d similar to 10 kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra. I has a thin, well-defined main sequence turnoff of intermediate age (similar to 5-6 Gyr) and metallicity ([Fe/H] = -0.9 dex). We measure statistically significant spreads in both the iron and alpha-element abundances of sigma([Fe/H]) = 0.13 +/- 0.02 dex and sigma([alpha/Fe]) = 0.09 +/- 0.03 dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H]-as well as its low [alpha/Fe], apparent [Fe/H] spread, and present-day low luminosity-suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.

引用

页数：16

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