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arXiv 2108.01100astro-ph.GAastro-ph.SR
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大麦云和Milky Way超高速恒星群的比较

Comparing hypervelocity star populations from the Large Magellanic Cloud and the Milky Way

Fraser A. Evans, Tommaso Marchetti, Elena Maria Rossi, Josephine F. W. Baggen, Sanne Bloot

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18 pages, 10 figures. Accepted for publication in MNRAS
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摘要：

我们预测并比较了从银河系中心和大麦云云中心喷射出的超高速星的分布和性质。在我们的模型中，HVS以恒定的速率喷射-在两个星系中相等-通过希尔斯机制，并在组合势中传播，其中LMC在其第一次坠落时绕MW运行。通过选择与麦哲伦云和银河系中平面分离良好的$m>2\, \mathrm{M_\odot}$ HVS，我们确定了模拟HVS，这些模拟HVS将在未来盖亚卫星和Vera C的数据发布中从恒星晕中的普通恒星中脱颖而出。鲁宾天文台的时空遗产巡天（LSST）。我们发现，在这些深的调查，LMC HVS将超过MW的一个因素$\sim 2.5$，HVS可以更容易地逃离较浅的潜在的LMC。假设HVS射血率为$10^{-4} \, \mathrm{yr^{-1}}$，在最终Gaia数据发布和LMC（MW）LSST中可检测到的HVS将分别编号为$125_{-12}^{+11}$（$50_{-8}^{+7}$）和$140_{-11}^{+10}$（$42_{-7}^{+6}$）。MW和LMC HVS群体表现出不同的运动学和空间分布。虽然大麦哲伦星云的HVS的总速度比较适中，银河系中心距离也比较大，但大麦哲伦星云的HVS的分布范围更广，包括在$500 \, \mathrm{km \ s^{-1}}$上方有一个突出的高速尾，其中至少包含了一半的恒星。这些预测是强大的对合理的变化的银河系的潜力和LMC中心黑洞的质量。

英文摘要：

We predict and compare the distributions and properties of hyper-velocity stars (HVSs) ejected from the centres of the Milky Way (MW) and the Large Magellanic Cloud (LMC). In our model, HVSs are ejected at a constant rate -- equal in both galaxies -- via the Hills mechanism and are propagated in a combined potential, where the LMC orbits the MW on its first infall. By selecting $m>2\, \mathrm{M_\odot}$ HVSs well-separated from the Magellanic Clouds and Galactic midplane, we identify mock HVSs which would stand out from ordinary stars in the stellar halo in future data releases from the Gaia satellite and the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). We find that in these deep surveys, LMC HVSs will outnumber MW ones by a factor $\sim 2.5$, as HVSs can more easily escape from the shallower potential of the LMC. At an assumed HVS ejection rate of $10^{-4} \, \mathrm{yr^{-1}}$, HVSs detectable in the final Gaia data release and LSST from the LMC (MW) will number $125_{-12}^{+11}$ ($50_{-8}^{+7}$) and $140_{-11}^{+10}$ ($42_{-7}^{+6}$), respectively. The MW and LMC HVS populations show different kinematics and spatial distributions. While LMC HVSs have more modest total velocities and larger Galactocentric distances clustered around those of the LMC itself, HVSs from the MW show broader distributions, including a prominent high-velocity tail above $500 \, \mathrm{km \ s^{-1}}$ that contains at least half of the stars. These predictions are robust against reasonable variation of the Galactic potential and of the LMC central black hole mass.

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