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arXiv 1001.4533astro-ph.COastro-ph.GA
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Brilliant Halo Galvanian是Galvanian的中心吗？

Are Brightest Halo Galaxies Central Galaxies?

Ramin A. Skibba, Frank C. van den Bosch, Xiaohu Yang, Surhud More, Houjun Mo, Fabio Fontanot

备注：
17 pages, 11 figures. Axes labels of Fig. 3 fixed
发表信息：
2011, MNRAS, 410, 417
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摘要：

一般认为，暗物质晕中的中央星系，即具有最低比势能的星系，也是最亮的晕星系（BHG），并且它静止地位于暗物质势阱的中心。中央星系范式（CGP）是天文学研究各个领域的一个基本假设。在本文中，我们测试的有效性CGP使用一个大的星系群星表构建从斯隆数字巡天。对于每一个组，我们计算两个统计，${\cal R}$和${\cal S}$，量化偏移的视线速度和投影位置的最亮的星系团相对于其他组成员。通过比较$|{\cal R}|$和$|{\cal S}|$的累积分布与从详细的模拟群目录中获得的累积分布，我们排除了CGP是正确的零假设。相反，数据表明，在所有质量为$M$的晕中，非零比例的$f_{\rm BNC}(M)$中，BHG不是中心星系，而是卫星星系。特别地，我们发现$f_{\rm BNC}$从低质量晕中$\sim 0.25$（$10^{12} h^{-1} {\rm M_{\odot}} \leq M \lsim 2 \times 10^{13} h^{-1}{\rm M_{\odot}}$）增加到大质量晕中的PDMATHAMV（$M \gsim 5 \times 10^{13} h^{-1} {\rm M_{\odot}}$）。我们发现，这些值的$f_{\rm BNC}$是令人不安的高相比，从晕占领统计和半分析模型的星系形成的预测。最后，我们讨论了非零的$f_{\rm BNC}(M)$的各种影响，强调从卫星运动学推断的晕质量。

英文摘要：

It is generally assumed that the central galaxy in a dark matter halo, that is, the galaxy with the lowest specific potential energy, is also the brightest halo galaxy (BHG), and that it resides at rest at the centre of the dark matter potential well. This central galaxy paradigm (CGP) is an essential assumption made in various fields of astronomical research. In this paper we test the validity of the CGP using a large galaxy group catalogue constructed from the Sloan Digital Sky Survey. For each group we compute two statistics, ${\cal R}$ and ${\cal S}$, which quantify the offsets of the line-of-sight velocities and projected positions of brightest group galaxies relative to the other group members. By comparing the cumulative distributions of $|{\cal R}|$ and $|{\cal S}|$ to those obtained from detailed mock group catalogues, we rule out the null-hypothesis that the CGP is correct. Rather, the data indicate that in a non-zero fraction $f_{\rm BNC}(M)$ of all haloes of mass $M$ the BHG is not the central galaxy, but instead, a satellite galaxy. In particular, we find that $f_{\rm BNC}$ increases from $\sim 0.25$ in low mass haloes ($10^{12} h^{-1} {\rm M_{\odot}} \leq M \lsim 2 \times 10^{13} h^{-1}{\rm M_{\odot}}$) to $\sim 0.4$ in massive haloes ($M \gsim 5 \times 10^{13} h^{-1} {\rm M_{\odot}}$). We show that these values of $f_{\rm BNC}$ are uncomfortably high compared to predictions from halo occupation statistics and from semi-analytical models of galaxy formation. We end by discussing various implications of a non-zero $f_{\rm BNC}(M)$, with an emphasis on the halo masses inferred from satellite kinematics.

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