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arXiv 1109.0010astro-ph.CO
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暗物质晕的积分恒星含量

The integrated stellar content of dark matter halos

Alexie Leauthaud, Matthew R. George, Peter S. Behroozi, Kevin Bundy, Jeremy Tinker, Risa H. Wechsler, Charlie Conroy, Alexis Finoguenov, Masayuki Tanaka

摘要:

对星系中恒星总量的测量,作为宿主晕质量的函数,包含了关于调节恒星形成过程效率的关键线索。我们用两种互补的方法导出了恒星总质量分数f_star随晕质量M_(500)c(z=0.2 ~ z=1)的变化关系。首先,我们推导出f_star使用统计Halo职业分布模型联合约束的数据从透镜,集群,和恒星质量函数。这种方法使我们能够探测f_star在更广泛的晕质量范围比集团或集群目录。其次,我们使用COSMOS X射线星表在群尺度上推导出f_star,并证明了两种方法的一致性在30%以内。我们用丰度匹配方法量化了f_star上的系统不确定性,我们表明,f_star上的统计不确定性(~10%)与恒星质量测量相关的系统不确定性(~45%,不包括IMF不确定性)相比相形见绌。假设一个夏布里耶IMF,我们发现在M500 c =10^13 Msun时0.012<f_star<0.025,在M500 c =10^14 Msun时0.0057<f_star<0.015。这些数值大大低于先前公布的估计数。我们调查这种差异的原因,并发现以前的工作高估了f_star由于不准确的恒星质量估计和/或因为他们假设所有星系的组中的早期类型的星系具有恒定的质光比的组合。与先前的说法相反,我们的结果表明,对于10^13 Msun以上的晕,f_star的平均值总是显著低于f_gas。结合我们的结果与最近发表的气体质量分数,我们发现在R500 c的f_star+f_gas相比,宇宙平均值的不足。这种不足随着晕质量的变化而变化,越低的晕质量越大。

英文摘要:

Measurements of the total amount of stars locked up in galaxies as a function of host halo mass contain key clues about the efficiency of processes that regulate star formation. We derive the total stellar mass fraction f_star as a function of halo mass M500c from z=0.2 to z=1 using two complementary methods. First, we derive f_star using a statistical Halo Occupation Distribution model jointly constrained by data from lensing, clustering, and the stellar mass function. This method enables us to probe f_star over a much wider halo mass range than with group or cluster catalogs. Second, we derive f_star at group scales using a COSMOS X-ray group catalog and we show that the two methods agree to within 30%. We quantify the systematic uncertainty on f_star using abundance matching methods and we show that the statistical uncertainty on f_star (~10%) is dwarfed by systematic uncertainties associated with stellar mass measurements (~45% excluding IMF uncertainties). Assuming a Chabrier IMF, we find 0.012<f_star<0.025 at M500c=10^13 Msun and 0.0057<f_star<0.015 at M500c=10^14 Msun. These values are significantly lower than previously published estimates. We investigate the cause of this difference and find that previous work has overestimated f_star due to a combination of inaccurate stellar mass estimators and/or because they have assumed that all galaxies in groups are early type galaxies with a constant mass-to-light ratio. Contrary to previous claims, our results suggest that the mean value of f_star is always significantly lower than f_gas for halos above 10^13 Msun. Combining our results with recently published gas mas fractions, we find a shortfall in f_star+f_gas at R500c compared to the cosmic mean. This shortfall varies with halo mass and becomes larger towards lower halos masses.

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