Constraints on the Distribution of Dark Matter within the Milky Way

人们普遍认为，我们银河系的大部分质量存在于一个或多个看不见的“黑暗”成分中。在没有直接探测的情况下，暗物质的分布可以通过观察其在银河系势能的适当示踪剂上的引力效应来绘制。对造父变星和K矮星这两种不同示踪剂的观测将用于确定(a)太阳到银河系中心的距离，(b)经过太阳附近的封闭轨道偏离轴对称，以及(c)太阳位置处银河系圆盘的质量表面密度。与轴对称的偏差将通过在银河系经度l = 60度方向寻找新的造父变星来获得，补充最近在l = 300度方向成功进行的搜索。随后的光度测量将在近红外波段1.2、1.6和2.2微米处进行，在那里星际消光的影响大大减少。

It is widely believed that most of the mass in our Galaxy lies in one or more unseen "dark" components. In the absence of direct detection, the distribution of dark matter can be mapped by observing its gravitational effects on suitably chosen tracers of the Milky Way's potential energy. Observations of two different tracers, Cepheid variable stars and K dwarfs, will be used to determine (a) the distance from the Sun to the center of the Galaxy, (b) the deviation from axisymmetry of the closed orbits passing near the Sun, and (c) the mass surface density of the disk of the Galaxy at the Sun's position. The deviation from axisymmetry will be obtained by way of a search for new Cepheids toward galactic longitude l = 60 degrees, complementing a recent successful search carried out toward l = 300 degrees. Followup photometry will be obtained in the near infrared at 1.2, 1.6, and 2.2 microns, where the effects of interstellar extinction are substantially reduced.