Exploring Halo Substructure with Giant Stars: The Velocity Dispersion Profiles of the Ursa Minor and Draco Dwarf Spheroidal Galaxies at Large Angular Separations
Exploring Halo Substructure with Giant Stars: The Velocity Dispersion Profiles of the Ursa Minor and Draco Dwarf Spheroidal Galaxies at Large Angular Separations
复制标题
探索巨星的光晕亚结构：小熊座和天龙座矮球状星系在大角距下的速度色散剖面
DOI：
10.1086/497396
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
M. Siegel
中科院分区：
文献类型：
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作者：
R. Muñoz;P. Frinchaboy;S. Majewski;J. Kuhn;M. Chou;C. Palma;S. Sohn;R. Patterson;M. Siegel
我们分析速度色散配置文件的天龙座和小熊座（UMi）矮球状（dSPH）星系的基础上公布的和新的凯克HIRES光谱的恒星在外部UMi领域。华盛顿+DDO 51滤光光度星表提供了对单个恒星成员的额外影响，在0.5 King极限半径（rlim）以上，识别真正的dSph成员的效率比简单的色星等图选择高4.5倍。以前报道的“冷人口”在rlim是不明显的数据，只出现特定的装箱;或多或少的常数和platykurtic色散曲线的特点，这些dSphs大半径。我们报告发现的UMi星至少为2.7rlim（即，210'或4 kpc）。即使在保守的假设下，UMi的质量需要大于4.9 × 108 M才能束缚这些恒星，这意味着M/L > 900（M/L）的整体质光比是不太可能的。我们的结论是，我们已经发现恒星潮汐剥离从UMi。
We analyze velocity dispersion profiles for the Draco and Ursa Minor (UMi) dwarf spheroidal (dSph) galaxies based on published and new Keck HIRES spectra for stars in the outer UMi field. Washington + DDO51 filter photometric catalogs provide additional leverage on membership of individual stars and, beyond 0.5 King limiting radii (rlim), identify bona fide dSph members up to 4.5 times more efficiently than simple color-magnitude diagram selections. Previously reported "cold populations" at rlim are not obvious in the data and appear only with particular binning; more or less constant and platykurtic dispersion profiles are characteristic of these dSphs to large radii. We report the discovery of UMi stars to at least 2.7rlim (i.e., 210' or 4 kpc). Even with conservative assumptions, a UMi mass of M > 4.9 × 108 M☉ is required to bind these stars, implying an unlikely global mass-to-light ratio of M/L > 900 (M/L)☉. We conclude that we have found stars tidally stripped from UMi.