arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1504.05591astro-ph.CO
收藏

作为物理晕边界的回溅半径与晕团的增长

The splashback radius as a physical halo boundary and the growth of halo mass

Surhud More, Benedikt Diemer, Andrey Kravtsov

备注：
15 pages, 12 figures, comments most welcome
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

冷暗物质晕的边界通常被定义为包含相对于参考（平均或临界）密度的密度对比$Δ$。我们认为，一个更物理的边界晕是半径吸积物质到达其第一个轨道远心后转向。这个回溅半径，$R_{sp}$，表现为在晕外围的密度急剧下降，在一个位置，取决于质量吸积率。我们目前的校准$R_{sp}$和封闭的质量，$M_{sp}$，作为吸积率的函数，或者峰高。我们发现$R_{sp}$在快速吸积晕的$\approx0.8-1R_{200m}$和缓慢吸积晕的$\approx1.5R_{200m}$之间变化。因此，晕圈的范围及其相关的环境影响可以远远超出传统定义的“维里”半径。我们发现，$M_{sp}$和$R_{sp}$发展相对较强的其他常用的定义相比。特别是，即使对于$z=0$中最小的矮型晕，$M_{sp}$也会发生显著的演化。我们还对比$M_{sp}$与质量封闭在四个规模半径的晕密度分布，$M_{<4rs}$，其特点是内晕。在晕组装的早期阶段，$M_{sp}$和$M_{<4rs}$演化相似，但在晚期阶段，$M_{<4rs}$停止增加，而$M_{sp}$继续显著增长。这说明，低$z$的晕可以有“安静”的内部，同时继续在其外围增加质量。我们讨论了潜在的观测估计的回溅半径，并表明它可能已经被发现在星系团。

英文摘要：

The boundaries of cold dark matter halos are commonly defined to enclose a density contrast $Δ$ relative to a reference (mean or critical) density. We argue that a more physical boundary of halos is the radius at which accreted matter reaches its first orbital apocenter after turnaround. This splashback radius, $R_{sp}$, manifests itself as a sharp density drop in the halo outskirts, at a location that depends upon the mass accretion rate. We present calibrations of $R_{sp}$ and the enclosed mass, $M_{sp}$, as a function of the accretion rate and alternatively peak height. We find that $R_{sp}$ varies between $\approx0.8-1R_{200m}$ for rapidly accreting halos and $\approx1.5R_{200m}$ for slowly accreting halos. The extent of a halo and its associated environmental effects can thus extend well beyond the conventionally defined "virial" radius. We show that $M_{sp}$ and $R_{sp}$ evolve relatively strongly compared to other commonly used definitions. In particular, $M_{sp}$ evolves significantly even for the smallest dwarf-sized halos at $z=0$. We also contrast $M_{sp}$ with the mass enclosed within four scale radii of the halo density profile, $M_{<4rs}$, which characterizes the inner halo. During the early stages of halo assembly, $M_{sp}$ and $M_{<4rs}$ evolve similarly, but in the late stages $M_{<4rs}$ stops increasing while $M_{sp}$ continues to grow significantly. This illustrates that halos at low $z$ can have "quiet" interiors while continuing to accrete mass in their outskirts. We discuss potential observational estimates of the splashback radius and show that it may already have been detected in galaxy clusters.

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。

↑