Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
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DOI：
10.1111/j.1365-2966.2007.12034.x
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发表时间：
2007-05
影响因子：
4.8
通讯作者：
Qingjuan Yu;P. Madau
中科院分区：
文献类型：
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作者：
Qingjuan Yu;P. Madau
与其他晕星相比，银河系中心大质量黑洞喷出的超高速星（HVS）具有独特的运动学特性。由于扁平圆盘和三轴暗物质晕产生的银河系势的不对称性，它们的轨道将偏离精确的径向，导致角动量的变化可能比注入时的初始小值大得多。我们研究了HVS的运动学，提出了一个仅由HVS在大银心距（r ≥ 50 kpc）下的瞬时位置和速度矢量确定的暗晕三轴度的估计。结果表明，在实质上为三轴晕的情况下，HVS在束缚轨道上的偏转角（恒星位置和速度矢量之间的夹角）分布在10°-180°范围内是均匀分布的.未来的天体测量和深宽视场巡天应该测量大量HVS的位置和速度，并对银河系暗物质晕的形状提供有用的约束。
Hypervelocity stars (HVSs) ejected by the massive black hole at the Galactic Centre have unique kinematic properties compared to other halo stars. Their trajectories will deviate from being exactly radial because of the asymmetry of the Milky Way potential produced by the flattened disc and the triaxial dark matter halo, causing a change of angular momentum that can be much larger than the initial small value at injection. We study the kinematics of HVSs and propose an estimator of dark halo triaxiality that is determined only by instantaneous position and velocity vectors of HVSs at large Galactocentric distances (r ≥ 50 kpc). We show that, in the case of a substantially triaxial halo, the distribution of deflection angles (the angle between the stellar position and velocity vector) for HVSs on bound orbits is spread uniformly over the range 10°-180°. Future astrometric and deep wide-field surveys should measure the positions and velocities of a significant number of HVSs, and provide useful constraints on the shape of the Galactic dark matter halo.