Mismatch between X-Ray and Emission-weighted Temperatures in Galaxy Clusters: Cosmological Implications
Mismatch between X-Ray and Emission-weighted Temperatures in Galaxy Clusters: Cosmological Implications
复制标题
星系团中 X 射线和发射加权温度之间的不匹配：宇宙学意义
DOI：
10.1086/427554
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
Osservatorio Astronomico di Pino Torinese
中科院分区：
文献类型：
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作者：
E. Rasia;P. Mazzotta;S. Borgani;L. Moscardini;K. Dolag;G. Tormen;A. Diaferio;G. Murante;U. Padova;Universita' di Roma Tor Vergata;Sao;Universita di UdineI.N.F.N. Trieste;Infn;U. Bologna;U. Torino;Osservatorio Astronomico di Pino Torinese
星系团流体动力学模拟的热学性质通常是通过发射加权温度Tew来与观测进行比较的，而不是依靠由实际观测数据获得的光谱X射线温度TSpec。在最近的一篇论文中，Mazzotta等人。证明如果星系团内的介质是热复杂的，Tew在复制TSpec时就失败了。他们提出了一个新的公式，类似光谱的温度TSL，它比TSPEC更接近几个百分点。通过分析一组星系团的流体动力学模拟，我们发现TSL比Tew低20%-30%。因此，模拟得到的M-TSL关系的归一化程度比观测到的要大50%左右。如果模拟星系团中的质量是按照同样的流体静力平衡和β模型气体密度分布的假设来估计的，就像通常对观测到的星系团所做的那样，那么M-T关系减少了大约40%，并且显著地减少了它的散布。根据这一结果，我们得出结论，用观测到的M-T关系从X射线温度函数推断功率谱的幅度可以使低σ8偏移10%-20%。这可能会缓解由星系团数密度推算的σ-8值与由宇宙微波背景和大尺度结构推算的值之间的紧张关系。
The thermal properties of hydrodynamical simulations of galaxy clusters are usually compared to observations by relying on the emission-weighted temperature Tew instead of on the spectroscopic X-ray temperature Tspec, which is obtained by actual observational data. In a recent paper, Mazzotta et al. show that if the intracluster medium is thermally complex, Tew fails at reproducing Tspec. They propose a new formula, the spectroscopic-like temperature, Tsl, which approximates Tspec better than a few percent. By analyzing a set of hydrodynamical simulations of galaxy clusters, we find that Tsl is lower than Tew by 20%-30%. As a consequence, the normalization of the M-Tsl relation from the simulations is larger than the observed one by about 50%. If masses in simulated clusters are estimated by following the same assumptions of hydrostatic equilibrium and β-model gas density profile, as is often done for observed clusters, then the M-T relation decreases by about 40% and significantly reduces its scatter. On the basis of this result, we conclude that using the observed M-T relation to infer the amplitude of the power spectrum from the X-ray temperature function could bias low σ8 by 10%-20%. This may alleviate the tension between the value of σ8 inferred from the cluster number density and those from the cosmic microwave background and large-scale structure.