A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM
A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM
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DOI：
10.1088/0004-637x/768/2/172
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发表时间：
2013-02
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通讯作者：
M. Collins;S. Chapman;R. Rich;R. Ibata;N. Martin;N. Martin;M. Irwin;N. Bate;G. Lewis;J. Peñarrubia;J. Peñarrubia;N. Arimoto;N. Arimoto;C. Casey;A. Ferguson;A. Koch;A. McConnachie;N. Tanvir
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作者：
M. Collins;S. Chapman;R. Rich;R. Ibata;N. Martin;N. Martin;M. Irwin;N. Bate;G. Lewis;J. Peñarrubia;J. Peñarrubia;N. Arimoto;N. Arimoto;C. Casey;A. Ferguson;A. Koch;A. McConnachie;N. Tanvir
我们用Keck I/LRIS和Keck II/DEIMOS光谱仪对28个仙女座矮球（dSph）星系中的18个星系中的红巨星分支恒星进行了均匀的运动学分析。根据它们的g−i颜色（用CFHT/MegaCam成像仪拍摄）、在天空中的物理位置和径向速度，我们为每颗观测到的恒星分配了dSph成员的概率。利用这些信息，计算出这些天体的速度色散、中心质量和暗物质晕的中心密度，并与银河系dSph群的特性进行比较。我们还从每个M31 dSph的成员星的共加光谱中测量了平均金属丰度（[Fe/H]），发现它们与在银河系中观测到的[Fe/H]随光度降低的趋势一致。我们发现我们研究的三个M31 dsph在中心速度色散方面表现出显著的异常值，以及XIX， XXI和XXV，它们都具有大的半光半径（≥700pc）和低的速度色散（σv < 5 km s−1）。此外，和XXV在其半光半径内的质量光比为，使其符合一个简单的恒星系统，在其1σ不确定度内没有明显的暗物质成分。我们认为这些异常值的暗物质晕的结构已经被潮汐显著地改变了。
We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g − i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii (≳ 700 pc) and low velocity dispersions (σv < 5 km s−1). In addition, And XXV has a mass-to-light ratio within its half-light radius of just , making it consistent with a simple stellar system with no appreciable dark matter component within its 1σ uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.