A NEW LOW MASS FOR THE HERCULES dSph: THE END OF A COMMON MASS SCALE FOR THE DWARFS?
A NEW LOW MASS FOR THE HERCULES dSph: THE END OF A COMMON MASS SCALE FOR THE DWARFS?
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DOI：
10.1088/0004-637x/706/1/l150
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发表时间：
2009-10
期刊：
影响因子：
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通讯作者：
D. Ad'en;M. Wilkinson;J. Read;S. Feltzing;A. Koch;G. Gilmore;E. Grebel;I. Lundström
中科院分区：
文献类型：
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作者：
D. Ad'en;M. Wilkinson;J. Read;S. Feltzing;A. Koch;G. Gilmore;E. Grebel;I. Lundström
我们基于 Adén 等人获得的修正后的速度色散，提出了大力神矮球状星系 (dSph) 的新质量估计。使用新获得的 Strömgren 光度测定法去除了显着的前景污染，从而降低了速度色散。使用这个新的速度色散 3.72 ± 0.91 km s-1，我们在中心 300 pc（也是半光半径）内发现质量为 M300 = 1.9+1.1−0.8 × 106 M☉，在我们的数据范围内到 433 pc，质量为 M433 = 3.7+2.2−1.6 × 106 M☉，明显低于之前的估计。我们得出总体质光比为 M433/L = 103+83−48[M☉/L☉]。我们的质量估计对最近关于 dSph 星系的共同质量尺度的说法提出了质疑。此外，我们在运动学数据中发现了 16 ± 3 km s−1 kpc−1 速度梯度的初步证据，以及~0.5 kpc 处光分布不对称延伸的证据。我们探索这些特征是否是由于潮汐与银河系的相互作用造成的。我们证明存在一个自洽模型，其中 Hercules 的假定潮汐半径为 rt = 485 pc，轨道近心为 rp = 18.5 ± 5 kpc，rt 内的质量为 。测试该模型需要适当的运动。尽管我们不能排除大力神不含暗物质的模型，但我们认为大力神更有可能是一个以暗物质为主的系统，目前其外部部分正在经历一些潮汐扰动。
We present a new mass estimate for the Hercules dwarf spheroidal (dSph) galaxy, based on the revised velocity dispersion obtained by Adén et al. The removal of a significant foreground contamination using newly acquired Strömgren photometry has resulted in a reduced velocity dispersion. Using this new velocity dispersion of 3.72 ± 0.91 km s-1, we find a mass of M300 = 1.9+1.1−0.8 × 106 M☉ within the central 300 pc, which is also the half-light radius, and a mass of M433 = 3.7+2.2−1.6 × 106 M☉ within the reach of our data to 433 pc, significantly lower than previous estimates. We derive an overall mass-to-light ratio of M433/L = 103+83−48[M☉/L☉]. Our mass estimate calls into question recent claims of a common mass scale for dSph galaxies. Additionally, we find tentative evidence for a velocity gradient in our kinematic data of 16 ± 3 km s−1 kpc−1, and evidence of an asymmetric extension in the light distribution at ∼0.5 kpc. We explore the possibility that these features are due to tidal interactions with the Milky Way. We show that there is a self-consistent model in which Hercules has an assumed tidal radius of rt = 485 pc, an orbital pericenter of rp = 18.5 ± 5 kpc, and a mass within rt of . Proper motions are required to test this model. Although we cannot exclude models in which Hercules contains no dark matter, we argue that Hercules is more likely to be a dark-matter-dominated system that is currently experiencing some tidal disturbance of its outer parts.