利用MilkyWay @home估算Orphan-Chenab流的矮星系祖先的质量和径向轮廓
Estimate of the Mass and Radial Profile of the Orphan-Chenab Stream's Dwarf Galaxy Progenitor Using MilkyWay@home
摘要：
我们适合的质量和径向轮廓的孤儿Chenab流（OCS）矮星系的祖先，通过使用斯隆数字巡天（SDSS）和暗能量相机（DEC）的关闭星约束N体模拟的OCS祖先落入银河系的1.5 PetaFLOPS MilkyWay@home分布式超级计算机。我们推断的内部结构的OCS的祖先的假设下，它是一个球对称的矮星系的恒星系统嵌入在一个扩展的暗物质晕。我们优化的演化时间，重子和暗物质的尺度半径，重子和暗物质质量的祖先使用差分进化算法。通过比较模拟的潮汐流与天空中观测到的OCS恒星的角分布来确定每组参数的似然分数。我们将OCS祖细胞的总质量与（$2.0\pm0.3$）$\times 10^7 M_\odot$拟合，其中$γ=73.5\pm10.6$和（$1.1\pm0.2$）$\times10^6M_{\odot}$的质光比在其中心的300 pc范围内。在其半光半径范围内，我们估计了（$4.0\pm1.0$）$\times10^5M_{\odot}$的总质量。我们还拟合了祖先遗迹的当前天空位置为$(α,δ)=((166.0\pm0.9)^\circ,(-11.1\pm2.5)^\circ)$，并表明它在目前是引力未结合的。测得的祖先质量是在以前的测量低端，如果证实降低超微弱矮星系的质量范围。我们的优化假设一个固定的银河系潜力，外大陆架轨道，和径向轮廓的祖先，忽略了大麦云云的影响。
英文摘要：
We fit the mass and radial profile of the Orphan-Chenab Stream's (OCS) dwarf galaxy progenitor by using turnoff stars in the Sloan Digital Sky Survey (SDSS) and the Dark Energy Camera (DEC) to constrain N-body simulations of the OCS progenitor falling into the Milky Way on the 1.5 PetaFLOPS MilkyWay@home distributed supercomputer. We infer the internal structure of the OCS's progenitor under the assumption that it was a spherically symmetric dwarf galaxy comprised of a stellar system embedded in an extended dark matter halo. We optimize the evolution time, the baryonic and dark matter scale radii, and the baryonic and dark matter masses of the progenitor using a differential evolution algorithm. The likelihood score for each set of parameters is determined by comparing the simulated tidal stream to the angular distribution of OCS stars observed in the sky. We fit the total mass of the OCS's progenitor to ($2.0\pm0.3$) $\times 10^7 M_\odot$ with a mass-to-light ratio of $γ=73.5\pm10.6$ and ($1.1\pm0.2$)$\times10^6M_{\odot}$ within 300 pc of its center. Within the progenitor's half-light radius, we estimate total a mass of ($4.0\pm1.0$)$\times10^5M_{\odot}$. We also fit the current sky position of the progenitor's remnant to be $(α,δ)=((166.0\pm0.9)^\circ,(-11.1\pm2.5)^\circ)$ and show that it is gravitationally unbound at the present time. The measured progenitor mass is on the low end of previous measurements, and if confirmed lowers the mass range of ultrafaint dwarf galaxies. Our optimization assumes a fixed Milky Way potential, OCS orbit, and radial profile for the progenitor, ignoring the impact of the Large Magellanic Cloud.
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