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arXiv 1310.2659astro-ph.GAhep-ph
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Milky Way旋转曲线，输出至$\sim$ 200 kpc

Rotation Curve of the Milky Way out to $\sim$ 200 kpc

Pijushpani Bhattacharjee, Soumini Chaudhury, Susmita Kundu

备注：
16 pages, 12 Figures; minor changes in Abstract, text, and some Figures; one reference added; main results unchanged; version accepted for publication in ApJ
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摘要：

我们的银河系的旋转曲线（RC）是从它的非常内部的区域（几百pc）开始，直到一个大的银心距离$\sim 200$ kpc，使用各种示踪物体在银河系引力势中移动的运动学数据来构建的，没有假设银河系的可见物质和暗物质成分的任何理论模型。我们研究了由于银河系常数（GC）$R_\odot$和$V_\odot$（这些是太阳的距离和围绕银河系中心的圆周旋转速度，分别）和速度各向异性参数$β$的光环示踪物用于推导RC在大银心距离的值的不确定性对RC的影响。由此产生的RC在磁盘区域被发现显着依赖于GC的选择，而在RC在大的距离以外的恒星盘的主要不确定性来自$β$的值的不确定性。一般来说，我们发现，平均RC稳定下降的距离超过$\sim 60$ kpc，独立的值的$β$。而且，在给定的半径处，对于较大的$β$值，圆周速度较低（即，对于更径向偏置的速度各向异性）。考虑到$β$的最大可能值是1，这对应于恒星轨道是纯径向的，我们的结果的情况下$β=1$给出了一个下限的总质量的银河系内的$\sim 200$ kpc，$M(200 {\rm kpc}) \gsim (6.8\pm4.1) \times 10^{11} M_\odot$，独立于任何模型的暗物质晕的银河系。

英文摘要：

The rotation curve (RC) of our Galaxy, the Milky Way, is constructed starting from its very inner regions (few hundred pc) out to a large Galactocentric distance of $\sim 200$ kpc using kinematical data on a variety of tracer objects moving in the gravitational potential of the Galaxy, without assuming any theoretical models of the visible and dark matter components of the Galaxy. We study the effect on the RC due to the uncertainties in the values of the Galactic Constants (GCs) $R_\odot$ and $V_\odot$ (these being the sun's distance from and circular rotation speed around the Galactic center, respectively) and the velocity anisotropy parameter $β$ of the halo tracer objects used for deriving the RC at large Galactocentric distances. The resulting RC in the disk region is found to depend significantly on the choice of the GCs, while the dominant uncertainty in the RC at large distances beyond the stellar disk comes from the uncertainty in the value of $β$. In general we find that the mean RC steadily declines at distances beyond $\sim 60$ kpc, independently of the value of $β$. Also, at a given radius, the circular speed is lower for larger values of $β$ (i.e., for more radially biased velocity anisotropy). Considering that the largest possible value of $β$ is unity, which corresponds to stellar orbits being purely radial, our results for the case of $β=1$ give a lower limit to the total mass of the Galaxy within $\sim 200$ kpc, $M(200 {\rm kpc}) \gsim (6.8\pm4.1) \times 10^{11} M_\odot$, independently of any model of the dark matter halo of the Galaxy.

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