卫星动力学I：一种约束中央星系晕质光关系的新方法
Satellite Kinematics I: A New Method to Constrain the Halo Mass-Luminosity Relation of Central Galaxies
摘要：
卫星运动学可以用来探测中央星系的暗物质晕的质量。为了测量具有足够信噪比的运动学，人们使用大量中心星系的卫星星系，这些星系根据相似的性质堆叠（例如，光度）。然而，一般来说，中心星系的光度与其宿主晕质量之间的关系将具有非零散射。因此，这种叠加导致不同质量的晕中卫星星系的运动学结合在一起，这使得数据的解释变得复杂。在本文中，我们提出了一个分析框架来模拟卫星运动学，适当考虑这种分散和各种选择效果。我们表明，在散射的晕质光关系的存在下，通常使用的卫星星系的速度色散不能用来推断一个独特的晕质光关系。特别是，我们证明了有一个退化之间的平均值和晕质光关系的散射。我们提出了一种新的技术，可以打破这种简并性，其中包括测量速度分散使用两种不同的加权方案：主机加权（每个中央星系得到相同的权重）和卫星加权（每个中央星系得到的权重与其卫星的数量成正比）。使用这两个加权方案获得的速度分散之间的比率是一个强大的功能的晕质量-光度关系的散射，因此可以用来推断一个独特的光和质量之间的关系从卫星星系的运动学。
英文摘要：
Satellite kinematics can be used to probe the masses of dark matter haloes of central galaxies. In order to measure the kinematics with sufficient signal-to-noise, one uses the satellite galaxies of a large number of central galaxies stacked according to similar properties (e.g., luminosity). However, in general the relation between the luminosity of a central galaxy and the mass of its host halo will have non-zero scatter. Consequently, this stacking results in combining the kinematics of satellite galaxies in haloes of different masses, which complicates the interpretation of the data. In this paper we present an analytical framework to model satellite kinematics, properly accounting for this scatter and for various selection effects. We show that in the presence of scatter in the halo mass-luminosity relation, the commonly used velocity dispersion of satellite galaxies can not be used to infer a unique halo mass-luminosity relation. In particular, we demonstrate that there is a degeneracy between the mean and the scatter of the halo mass-luminosity relation. We present a new technique that can break this degeneracy, and which involves measuring the velocity dispersions using two different weighting schemes: host-weighting (each central galaxy gets the same weight) and satellite-weighting (each central galaxy gets a weight proportional to its number of satellites). The ratio between the velocity dispersions obtained using these two weighting schemes is a strong function of the scatter in the halo mass-luminosity relation, and can thus be used to infer a unique relation between light and mass from the kinematics of satellite galaxies.
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