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arXiv 0904.1983astro-ph.CO
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作为宇宙学探针的星系团对X射线背景的贡献

Cluster contribution to the X-ray background as a cosmological probe

Doron Lemze, Sharon Sadeh, Yoel Rephaeli

摘要:

对X射线背景(XRB)的广泛测量产生了其基本性质的合理可靠的表征。在将大部分宇宙XRB分解为离散源之后,其主要成分的能级和光谱形状可以用来探测源种群以及替代的宇宙学和大尺度结构模型。最近的观察集群似乎提供证据表明,集群形成更早,更丰富的标准$Λ$ CDM模型中预测的。这激发了人们对预测集群规模增强能力的替代模型的兴趣。我们计算预测的水平和光谱的叠加发射从集团和星系团在$Λ$ CDM和两个可行的替代非高斯($χ^2$)和早期的暗能量模型。在非高斯模型中,簇对XRB的贡献的预测水平超过了在低能量下的测量水平和在2-8 keV带中的残余XRB的水平;这些特定的模型基本上被排除。我们的工作证明了诊断价值的综合X射线发射的集群,也考虑其依赖于不同的金属丰度,气体和温度分布,银河系吸收,合并的情况下,和非热压力组件。我们还表明,XRB可以用于浓度参数值的上限。

英文摘要:

Extensive measurements of the X-ray background (XRB) yield a reasonably reliable characterisation of its basic properties. Having resolved most of the cosmic XRB into discrete sources, the levels and spectral shapes of its main components can be used to probe both the source populations and also alternative cosmological and large-scale structure models. Recent observations of clusters seem to provide evidence that clusters formed earlier and are more abundant than predicted in the standard $Λ$CDM model. This motivates interest in alternative models that predict enhanced power on cluster scales. We calculate predicted levels and spectra of the superposed emission from groups and clusters of galaxies in $Λ$CDM and in two viable alternative non-Gaussian ($χ^2$) and early dark energy models. The predicted levels of the contribution of clusters to the XRB in the non-Gaussian models exceed the measured level at low energies and levels of the residual XRB in the 2-8 keV band; these particular models are essentially ruled out. Our work demonstrates the diagnostic value of the integrated X-ray emission from clusters, by considering also its dependences on different metallicities, gas and temperature profiles, Galactic absorption, merger scenarios, and on a non-thermal pressure component. We also show that the XRB can be used for a upper limit for the concentration parameter value.

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