Estimating the Mass of the Milky Way Using the Ensemble of Classical Satellite Galaxies
Estimating the Mass of the Milky Way Using the Ensemble of Classical Satellite Galaxies
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DOI：
10.3847/1538-4357/aab78f
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发表时间：
2018-03
期刊：
影响因子：
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通讯作者：
E. Patel;G. Besla;K. Mandel;S. Sohn
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文献类型：
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作者：
E. Patel;G. Besla;K. Mandel;S. Sohn
在银河系所有已知的矮小卫星星系中，约有20%可以获得高精度的自行(PM)测量。在这里，我们扩展了Patel等人的贝叶斯框架。包括所有具有测量的6D相空间信息的毫米波卫星，并将其与Illustris-Dark模拟一起应用以约束毫米波的质量。单独使用每颗中波卫星的特性，我们发现，当采用特定轨道角动量(J)的大小时，质量估计之间的散布减小，而不是它们的瞬时位置和速度的组合。我们还发现，高j卫星(即，LEO II)限制了MW的质量上限，而低j卫星，而不是最高速度的卫星(即，Leo I和大麦哲伦星云)设定了质量下限。当用所有经典卫星的j来同时估计MW的质量时，我们得出晕质量为0.85+0.23−0.26×1012(包括人马座dSph)和0.96+0.29−0.28×1012(不包括人马座dSph)，并警告说像人马dSph这样衰变轨道上的低j卫星可能会偏离分布。这些估计显著地降低了微波质量范围内的两个扩散的电流系数。我们还发现了宿主晕质量和卫星j分布之间的明确关系，这给出了即将到来的超弱矮星PM的预测，j应该在5×10~3-104kpc公里的S−1内。随着更多的卫星PM的出现，这是一个很有希望的方法，可以显著限制宇宙学上预期的MW和最终M31的质量范围。
High precision proper motion (PM) measurements are available for approximately 20% of all known dwarf satellite galaxies of the Milky Way (MW). Here we extend the Bayesian framework of Patel et al. to include all MW satellites with measured 6D phase-space information and apply it with the Illustris-Dark simulation to constrain the MW’s mass. Using the properties of each MW satellite individually, we find that the scatter among mass estimates is reduced when the magnitude of specific orbital angular momentum (j) is adopted, rather than their combined instantaneous positions and velocities. We also find that high j satellites (i.e., Leo II) constrain the upper limits for the MW’s mass and low j satellites, rather than the highest speed satellites (i.e., Leo I and Large Magellanic Cloud), set the lower mass limits. When j of all classical satellites is used to simultaneously estimate the MW’s mass, we conclude the halo mass is 0.85+0.23−0.26 × 1012 (including Sagittarius dSph) and 0.96+0.29−0.28 × 1012 (excluding Sagittarius dSph), cautioning that low j satellites on decaying orbits like Sagittarius dSph may bias the distribution. These estimates markedly reduce the current factor of two spread in the mass range of the MW. We also find a well-defined relationship between host halo mass and satellite j distribution, which yields the prediction that upcoming PMs for ultra-faint dwarfs should reveal j within 5 × 103–104 kpc km s−1. This is a promising method to significantly constrain the cosmologically expected mass range for the MW and eventually M31 as more satellite PMs become available.