The Effect of Merger Boosts on the Luminosity, Temperature, and Inferred Mass Functions of Clusters of Galaxies
The Effect of Merger Boosts on the Luminosity, Temperature, and Inferred Mass Functions of Clusters of Galaxies
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DOI：
10.1086/342239
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发表时间：
2002-06
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影响因子：
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通讯作者：
S. Randall;C. Sarazin;P. Ricker
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文献类型：
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作者：
S. Randall;C. Sarazin;P. Ricker
在标准的冷暗物质结构形成模型中，大质量的星团是由较小的星团合并形成的。合并星系团的n体/流体动力学模拟表明，合并可以暂时提高合并星系团的x射线光度和温度，高于合并系统的平衡值。这些“合并助推”的累积效应将影响观测到的星团的x射线光度函数（XLFs）和温度函数（TFs）。人们预计这种效应对最明亮和最热的星团最为重要。星团的XLFs和TFs提供了一些对宇宙学和大尺度结构参数的最强约束，如平均涨落参数σ8和物质密度除以临界密度Ω0。如果假设虚拟均衡，合并效应会使从集群XLFs和TFs推断出的σ8和Ω0值产生偏差。我们使用半解析技术来估计合并提升对XLFs和TFs的影响。单个合并产生的推力来自于合并的n体/流体动力学模拟。集群的合并历史统计是由扩展的Press-Schechter （PS）合并树确定的。我们发现，合并促进可以增加热发光星团的表观数量。例如，在红移为z = 1的Ω0 = 0.3和ΩΛ = 0.7的宇宙中，温度为T >0 keV的星团数量增加了9.5倍，光度为LX bbb5 × 1044 h-2 ergs -1的星团数量增加了8.9倍。我们利用合并推进的TFs和XLFs，通过拟合PS平衡关系到局域（z = 0）和远域（z = 0.5或z = 1）的聚类样本，推导出了宇宙学结构参数σ8和Ω0。合并导致σ8被高估了约20%。物质密度参数Ω0可能被低估了约20%，尽管这个结果不太清楚。如果波动谱的参数是从观测到的TF或XLF（例如，从低红移样本）推导出来的，那么这就消除了Ω0上的大部分升压效应。然而，当将星团XLFs和TFs与其他技术（例如宇宙微波背景波动或遥远超新星的亮度）得出的宇宙结构参数进行比较时，可能会出现更大的合并促进效应。
In the standard cold dark matter model of structure formation, massive clusters form via the merger of smaller clusters. N-body/hydrodynamical simulations of merging galaxy clusters have shown that mergers can temporarily boost the X-ray luminosity and temperature of the merged cluster above the equilibrium values for the merged system. The cumulative effect of these "merger boosts" will affect the observed X-ray luminosity functions (XLFs) and temperature functions (TFs) of clusters. One expects this effect to be most important for the most luminous and hottest clusters. XLFs and TFs of clusters provide some of the strongest constraints on cosmological and large-scale structure parameters, such as the mean fluctuation parameter σ8 and the matter density divided by the critical density Ω0. Merger boosts may bias the values of σ8 and Ω0 inferred from cluster XLFs and TFs if virial equilibrium is assumed. We use a semianalytic technique to estimate the effect of merger boosts on the XLFs and TFs. The boosts from individual mergers are derived from N-body/hydrodynamical simulations of mergers. The statistics of the merger histories of clusters are determined from extended Press-Schechter (PS) merger trees. We find that merger boosts can increase the apparent number of hot, luminous clusters. For example, in a universe with Ω0 = 0.3 and ΩΛ = 0.7 at a redshift of z = 1, the number of clusters with temperatures T > 10 keV is increased by a factor of 9.5, and the number of clusters with luminosities LX > 5 × 1044 h-2 ergs s-1 is increased by a factor of 8.9. We have used our merger-boosted TFs and XLFs to derive the cosmological structure parameters σ8 and Ω0 by fitting PS equilibrium relations to local (z = 0) and distant (either z = 0.5 or z = 1) cluster samples. Merger boosts cause σ8 to be overestimated by about 20%. The matter density parameter Ω0 may be underestimated by about 20%, although this result is less clear. If the parameters of the fluctuation spectrum are derived from the observed TF or XLF (e.g., from a low-redshift sample), then this removes most of the boost effect on Ω0. However, larger merger boost effects may appear when cluster XLFs and TFs are compared to cosmological structure parameters derived by other techniques (e.g., cosmic microwave background fluctuations or the brightness of distant supernovae).