有组织的混沌：小星系中恒星质量与晕质量关系中的散射
Organized Chaos: Scatter in the relation between stellar mass and halo mass in small galaxies
摘要：
我们使用本星系群计数和ELVIS N体模拟来探索低质量恒星质量与晕质量关系中的散射和斜率之间的关系，$M_\star \simeq 10^5 - 10^8 M_\odot$。假设模型具有关于$M_\star \propto M_\mathrm{halo}^α$形式的中位数关系的对数正态分散，则首选的对数斜率从零分散极限的$α\simeq 1.8$陡峭到固定晕质量下$M_\star$中分散的$2$ dex的情况下的$α\simeq 2.6$。我们提供了最佳拟合关系的拟合函数作为分散的函数，包括关系随着质量的降低而变得越来越随机的情况。我们表明，如果分散在固定的晕质量是足够大的（$\gtrsim 1$ dex），如果中位数的关系是足够陡峭的（$α\gtrsim 2$），那么“太大而不能倒”的问题，在本地组可以自洽地消除约$\sim 5-10\%$的实现。这种情况下，需要最大的subhalos主机不可观测的超暗矮星相当频繁，我们讨论这些系统的潜在可观测的签名。最后，我们比较我们的衍生约束最近的高分辨率模拟矮星系形成的文献。虽然在固定的$M_\mathrm{halo}$下，$M_\star$中的模拟到模拟的散射在不同的作者之间是很大的（$\sim 2$ dex），但是单个代码产生的关系具有更小的散射，并且通常给出会过度产生局部星系计数的关系。
英文摘要：
We use Local Group galaxy counts together with the ELVIS N-body simulations to explore the relationship between the scatter and slope in the stellar mass vs. halo mass relation at low masses, $M_\star \simeq 10^5 - 10^8 M_\odot$. Assuming models with log-normal scatter about a median relation of the form $M_\star \propto M_\mathrm{halo}^α$, the preferred log-slope steepens from $α\simeq 1.8$ in the limit of zero scatter to $α\simeq 2.6$ in the case of $2$ dex of scatter in $M_\star$ at fixed halo mass. We provide fitting functions for the best-fit relations as a function of scatter, including cases where the relation becomes increasingly stochastic with decreasing mass. We show that if the scatter at fixed halo mass is large enough ($\gtrsim 1$ dex) and if the median relation is steep enough ($α\gtrsim 2$), then the "too-big-to-fail" problem seen in the Local Group can be self-consistently eliminated in about $\sim 5-10\%$ of realizations. This scenario requires that the most massive subhalos host unobservable ultra-faint dwarfs fairly often; we discuss potentially observable signatures of these systems. Finally, we compare our derived constraints to recent high-resolution simulations of dwarf galaxy formation in the literature. Though simulation-to-simulation scatter in $M_\star$ at fixed $M_\mathrm{halo}$ is large among separate authors ($\sim 2$ dex), individual codes produce relations with much less scatter and usually give relations that would over-produce local galaxy counts.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
