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arXiv 1706.02463astro-ph.CO
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星系群数密度分布图：“单晕”项NFW是否超出了$>10$维里半径？

Group galaxy number density profiles far out: is the 'one-halo' term NFW out to $>10$ virial radii?

Marina Trevisan, Gary A. Mamon, Diego H. Stalder

备注：
5 pages, 4 figures. Accepted for publication in MNRAS Letters. Final version including discussion on the backsplash radius
发表信息：
MNRAS 471, L47-51 (2017)
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摘要：

虽然$Λ$ CDM晕的密度分布（DP）在大约一个维里半径（$r_{\rm vir}$）范围内遵守NFW定律，但对其外部结构的了解仍然很少，因为描述晕本身的1-晕项由代表其他晕的2-晕项主导。使用半解析模型，我们测量实空间的“1-halo”数DP的组出$20\,r_{\rm vir}$分配每个星系到其最近的组与质量以上$M_{\rm a}$，在组$r_{\rm vir}$的单位。如果$M_{\rm a}$小（大），则组的外部DP快速（缓慢）下降。我们发现，有一个最佳的$M_{\rm a}$的堆叠DP类似的NFW模型$0.1$指数精度出$\simeq 13\,r_{\rm vir}$。我们发现类似的远程NFW表面DP（出$\simeq 10\,r_{\rm vir}$）在SDSS观测使用星系分配方案，结合非线性维里化区域的群体与他们的线性外部部分。最佳$M_{\rm a}$按堆叠到$0.25-0.3$幂的组的最小质量进行缩放。我们的研究结果表明，NFW模型并不完全起源于暴力松弛。此外，使用HOD模型填充星系晕必须进行到比通常更大的半径。

英文摘要：

While the density profiles (DPs) of $Λ$CDM haloes obey the NFW law out to roughly one virial radius, $r_{\rm vir}$, the structure of their outer parts is still poorly understood, since the 1-halo term describing the halo itself is dominated by the 2-halo term representing the other haloes picked up. Using a semi-analytical model, we measure the real-space `1-halo' number DP of groups out to $20\,r_{\rm vir}$ by assigning each galaxy to its nearest group with mass above $M_{\rm a}$, in units of the group $r_{\rm vir}$. If $M_{\rm a}$ is small (large), the outer DP of groups falls rapidly (slowly). We find that there is an optimal $M_{\rm a}$ for which the stacked DP resembles the NFW model to $0.1$ dex accuracy out to $\simeq 13\,r_{\rm vir}$. We find similar long-range NFW surface DPs (out to $\simeq 10\,r_{\rm vir}$) in the SDSS observations using a galaxy assignment scheme that combines the non-linear virialized regions of groups with their linear outer parts. The optimal $M_{\rm a}$ scales as the minimum mass of the groups that are stacked to the power $0.25-0.3$. Our results suggest that the NFW model does not solely originate from violent relaxation. Moreover, populating haloes with galaxies using HOD models must proceed out to larger radii than usually done.

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