The similarity of the stellar mass fractions of galaxy groups and clusters
The similarity of the stellar mass fractions of galaxy groups and clusters
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DOI：
10.1093/mnras/stt1965
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发表时间：
2013-09
影响因子：
4.8
通讯作者：
J. M. Budzynski;Sergey E. Koposov;I. McCarthy;V. Belokurov
中科院分区：
文献类型：
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作者：
J. M. Budzynski;Sergey E. Koposov;I. McCarthy;V. Belokurov
我们在SDSS中使用了20171个光学选择的群和星团的大样本来研究堆积的恒星质量分数在总质量的大范围内是如何变化的。我们的研究在许多重要方面改进了以前的观测研究，包括有更大的样本量，明确包括星系团内光(ICL)分量，以及通过与模拟和弱透镜观测的比较彻底检查我们总质量估计的准确性。我们发现恒星质量分数与总质量的关系很弱，ICL对恒星总质量分数的贡献很大(通常为20%-40%)。这两个发现都与宇宙学模拟的预测非常一致。在Chabrier(Salpeter)IMF的假设下，导出的恒星形成效率($f_(Star)$/$f_(B)$，其中$f_b=\omga_b/\omegga_m$)相对较低，为8%(14%)，与再现星系恒星质量函数的半解析模型的全球恒星形成效率是一致的。当我们测量的恒星质量分数与从X射线观测中观察到的热气体质量分数与总质量之间的关系结合起来时，我们的结果表明，星系群的重子分数明显低于大质量星系团。高能活动星系核反馈(最有可能是高红移)的气体喷射为解释我们观察到的趋势提供了一种合理的机制。
We employ a large sample of 20171 optically-selected groups and clusters at 0.15 < z < 0.4 in the SDSS to investigate how the stacked stellar mass fraction varies across a wide range of total mass, $M_{500}$. Our study improves upon previous observational studies in a number of important ways, including having a much larger sample size, an explicit inclusion of the intracluster light (ICL) component, and a thorough examination of the accuracy of our total mass estimates via comparisons to simulations and weak lensing observations. We find that the stellar mass fraction depends only weakly on total mass and that the contribution of ICL to the total stellar mass fraction is significant (typically 20-40 per cent). Both of these findings are in excellent accordance with the predictions of cosmological simulations. Under the assumption of a Chabrier (Salpeter) IMF, the derived star formation efficiency ($f_{star}$/$f_{b}$, where $f_b=\Omega_b/\Omega_m$) is relatively low at 8 per cent (14 per cent) and is consistent with the global star formation efficiency of semi-analytic models that reproduce the galaxy stellar mass function. When our measured stellar mass fractions are combined with the observed relation between hot gas mass fraction and total mass from X-ray observations, our results imply that galaxy groups have significantly lower baryon fractions than massive clusters. Ejection of gas due to energetic AGN feedback (most likely at high redshift) provides a plausible mechanism for explaining the trends we observe.