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arXiv 0904.2740astro-ph.CO
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作为宇宙学探测器的团簇气体质量分数:修正研究

The cluster gas mass fraction as a cosmological probe: a revised study

S. Ettori, A. Morandi, P. Tozzi, I. Balestra, S. Borgani, P. Rosati, L. Lovisari, F. Terenziani

摘要:

本文分析了用Chandra观测的52个X射线发光星系团在红移0.3-1.273范围内的重子含量。我们使用去投影的X射线表面亮度轮廓和气体温度的测量值来恢复气体和总质量轮廓。通过假设星系团代表宇宙重子收支,用最热(T> 4keV)系统中星系团重子分数随红移的分布来约束宇宙学参数。我们讨论了我们的约束是如何影响的几个系统学,即等温线,假设的重子分数的恒星,耗尽参数和样品的选择。通过仅使用星团重子分数作为宇宙学参数的代理,我们得到Ω被很好地限制在0.35的值,相对统计不确定度为11%(1 σ水平; w=-1),进一步的系统误差约为(-6,+7)%。另一方面,由于存在更大的统计和系统不确定性(Lambda的数量级为40%,w的数量级大于50%),对Lambda(没有平坦几何的先验)和w(使用平坦几何的先验)的约束肯定更弱。如果WMAP 5年的最佳拟合结果被假定为固定的宇宙学参数,我们限制的贡献,预计从非热压力的支持和ICM团块低于约10%,也留下空间,以容纳重子不占无论是在X射线发射等离子体或恒星的顺序的18%的总集群重子预算。

英文摘要:

(Abriged) We present the analysis of the baryonic content of 52 X-ray luminous galaxy clusters observed with Chandra in the redshift range 0.3-1.273. We use the deprojected X-ray surface brightness profiles and the measured values of the gas temperature to recover the gas and total mass profiles. By assuming that galaxy clusters are representative of the cosmic baryon budget, the distribution of the cluster baryon fraction in the hottest (T> 4 keV) systems as a function of redshift is used to constrain the cosmological parameters. We discuss how our constraints are affected by several systematics, namely the isothermality, the assumed baryon fraction in stars, the depletion parameter and the sample selection. By using only the cluster baryon fraction as a proxy for the cosmological parameters, we obtain that Omega is very well constrained at the value of 0.35 with a relative statistical uncertainty of 11% (1 sigma level; w=-1) and a further systematic error of about (-6,+7)%. On the other hand, constraints on Lambda (without the prior of flat geometry) and w (using the prior of flat geometry) are definitely weaker due to the presence of larger statistical and systematic uncertainties (of the order of 40 per cent on Lambda and larger than 50 per cent on w). If the WMAP 5-year best-fit results are assumed to fix the cosmological parameters, we limit the contributions expected from non-thermal pressure support and ICM clumpiness to be lower than about 10 per cent, leaving also room to accommodate baryons not accounted for either in the X-ray emitting plasma or in stars of the order of 18 per cent of the total cluster baryon budget.

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