论文标题
恒星光环中的径向运动能否限制银河系中质量的变化率？
Can radial motions in the stellar halo constrain the rate of change of mass in the Galaxy?
论文作者
论文摘要
随着时间的流逝，星系的质量发生变化将使其恒星运动的烙印留下痕迹，恒星径向向外（质量损失）或内向（质量积聚）散装运动。在这里，我们测试了使用恒星光环中恒星的平均径向运动来限制星系中质量变化速率的可行性，例如，由于暗物质的腐烂到无形的黑暗扇形颗粒或更保守的baryons粒子。在当前的$λ$ CDM结构形成范式中，恒星光环是通过将卫星积聚到主机银河系上的。随着时间的流逝，随着卫星的破坏和相位混合，恒星光环的平均径向运动$ \ langle v_ {r} \ rangle $最终预计将接近零。但是，由于特定积聚事件的不完整混合，大多数光晕都有子结构，这可能导致非零$ \ langle v_ {r} {r} \ rangle $在其中。使用模拟，我们测量平均径向运动，$ \ langle v_ {r} \ rangle $，13 $λ$ cdm cdm恒星光晕，位于半径为30 kpc的球形外壳中。我们发现，对于大多数光环，壳运动非常小，有75 \％的Halos具有$ \ langle v_ {r} \ rangle \ langle \ sillssim 1.2 \ {\ rm km km} s^{ - 1} $。当使用聚类算法删除子结构时，$ \ langle v_ {r} \ rangle $进一步减少，其中75 \％的Halos具有$ \ langle v_ {r} \ rangle \ rangle \ langle \ lyssim \ sillsim 0.6 \ sim \ lyssim 0.6 \ {\ rm km km km km} s^s^ - 1} $。 $ \ langle v_ {r} \ rangle \大约0.6 \ {\ rm km} s^{ - 1} $的值可以与银河系质量损失率相对应2 \％\％。我们表明，这可以对暗物质衰减参数（例如衰减生命周期和赋予子粒子的踢速度）施加约束。涉及数百万美元到数十亿颗恒星的全天候恒星调查的出现令人鼓舞，这很鼓励检测暗物质腐烂的签名。
A change in the mass of the Galaxy with time will leave its imprint on the motions of the stars, with stars having radially outward (mass loss) or inward (mass accretion) bulk motions. Here we test the feasibility of using the mean radial motion of stars in the stellar halo to constrain the rate of change of mass in the Galaxy, for example, due to decay of dark matter into invisible dark sector particles or more conservatively from the settling of baryons. In the current $Λ$CDM paradigm of structure formation, the stellar halo is formed by accretion of satellites onto the host galaxy. Over time, as the satellites disrupt and phase mix, the mean radial motion $\langle V_{R} \rangle$ of the stellar halo is eventually expected to be close to zero. But most halos have substructures due to incomplete mixing of specific accretion events and this can lead to nonzero $\langle V_{R} \rangle$ in them. Using simulations, we measure the mean radial motion, $\langle V_{R} \rangle$, of stars in 13 $Λ$CDM stellar halos lying in a spherical shell of radius 30 kpc. We find that for most halos, the shell motion is quite small, with 75\% of halos having $\langle V_{R}\rangle \lesssim 1.2 \ {\rm km}s^{-1}$. When substructures are removed by using a clustering algorithm, $\langle V_{R}\rangle$ is reduced even further, with 75\% of halos having $\langle V_{R}\rangle \lesssim 0.6 \ {\rm km}s^{-1}$. A value of $\langle V_{R}\rangle \approx 0.6 \ {\rm km}s^{-1}$ can be attained corresponding to a galactic mass loss rate of 2\% per Gyr. We show that this can place constraints on dark matter decay parameters such as the decay lifetime and the kick velocity that is imparted to the daughter particle. The advent of all-sky stellar surveys involving millions to billions of stars is encouraging for detecting signatures of dark matter decay.
