Measuring the Density Fluctuation from the Cluster Gas Mass Function
Measuring the Density Fluctuation from the Cluster Gas Mass Function
复制标题
从团簇气体质量函数测量密度波动
DOI：
10.1086/304805
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
K. Shimasaku
中科院分区：
文献类型：
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作者：
K. Shimasaku
为了测量星系团尺度上的密度涨落谱，我们导出了星系团的气体质量函数。从气体质量函数出发计算了富星系团中的重子丰度，并与大爆炸核合成理论预言的宇宙中的平均重子密度进行了比较。这个重子分数和气体质量函数的斜率限制了σ8和涨落谱的斜率，σ 8是8 h-1 Mpc尺度上的均方根线性涨落，其中h是哈勃常数，单位为100 km s-1 Mpc-1。采用重子的密度参数Ω B 0 h 2 =0.0175±0.0075（误差在1 σ水平），当h = 0.5时，我们得到（σ8，n）=（0.64+ 0.18−0.09，-1.6+ 1.1−0.4）;当h = 0.8时，我们得到（σ8，n）=（0.73+ 0.27−0.11，-1.5+ 1.2−0.4）。较高的h给出较高的σ8，而较高的Ω B 0给出较低的σ8。σ8和n中的误差包含Ω B 0和观测气体质量函数中的1 σ误差。我们假设密度谱近似于簇尺度上的幂律σ（r）<$r-（3 + n）/2。我们的σ8值与密度参数Ω0无关，因此我们可以通过将本研究中获得的σ8值与迄今为止其他依赖于Ω0的分析结果相结合来估计Ω0。我们发现，由星系团丰度（如温度函数）导出的σ8（Ω0）给出Ω0 ~ 0.7，而由星系特有速度场测量的σ8（Ω0）给出Ω0 ~ 0.3-1.3，这取决于分析星系特有速度数据所采用的技术。约束条件也来自三套冷暗物质模型和一套冷+热暗物质模型。
We derive the gas mass function of clusters of galaxies in order to measure the density fluctuation spectrum on cluster scales. The baryon abundance confined in rich clusters is computed from the gas mass function and compared with the mean baryon density in the universe predicted by big bang nucleosynthesis. This baryon fraction and the slope of the gas mass function put constraints on σ8, the rms linear fluctuation on scales of 8 h-1 Mpc, where h is the Hubble constant in units of 100 km s-1 Mpc-1, and on the slope of the fluctuation spectrum. Adopting the density parameter of baryons ΩB0 h2=0.0175±0.0075 (errors are at 1 σ levels), we find (σ8, n)=(0.64+ 0.18−0.09, -1.6+ 1.1−0.4) for h = 0.5 and (σ8, n)=(0.73+ 0.27−0.11, -1.5+ 1.2−0.4) for h = 0.8. A higher h gives a higher σ8, while a higher ΩB0 gives a lower σ8. The errors in σ8 and n contain the 1 σ errors in ΩB0 and in the observed gas mass function. We assume that the density spectrum is approximated by a power law on cluster scales, σ(r) ∝ r-(3 + n)/2. Our value of σ8 is independent of the density parameter, Ω0, and thus we can estimate Ω0 by combining the value of σ8 obtained in this study with those from other, Ω0-dependent analyses to date. We find that σ8(Ω0) derived from cluster abundance, such as the temperature function, gives Ω0 ~ 0.7, while σ8(Ω0) measured from the peculiar velocity field of galaxies gives Ω0 ~ 0.3-1.3, depending on the technique used to analyze the peculiar velocity data. Constraints are also derived for three sets of cold dark matter models and a set of cold + hot dark matter models.