[论文解读] A Lensing Survey of X-ray Luminous Galaxy Clusters at Redshift z ~ 0.2: II: CFH12k Weak Lensing Analysis and Global Correlations

Sébastien Bardeau, G. Soucail+6 more|ArXiv.org|Mar 15, 2007

Galaxies: Formation, Evolution, Phenomena被引用 51

一句话总结

本研究利用CFH12k成像对红移z ~ 0.2的11个X射线明亮星系团进行了弱引力透镜分析，独立于X射线假设测量了总质量和质量分布。结果发现质量–X射线光度关系的标度关系为L_X ∝ M_200^{0.83±0.11}，归一化值与流体动力学模拟一致，表明演化程度较低，且显著的动态散射可能与并合历史有关。

ABSTRACT

Aims: We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. Methods: The eleven clusters in our sample are all X-ray luminous and span a narrow redshift range at z=0.21 +/- 0.04. The weak lensing analysis of the sample is based on ground-based wide-field imaging obtained with the CFH12k camera on CFHT. We use the methodology developed and applied previously on the massive cluster Abell 1689. A Bayesian method, implemented in the Im2shape software, is used to fit the shape parameters of the faint background galaxies and to correct for PSF smearing. With the present data, shear profiles are measured in all clusters out to at least 2 Mpc (more than 15arcmin from the center) with high confidence. The radial shear profiles are fitted with different parametric mass profiles and the virial mass M_200 is estimated for each cluster and then compared to other physical properties. Results: Scaling relations between mass and optical luminosity indicate an increase of the M/L ratio with luminosity and a L_X-M_200 relation scaling as L_X \propto M_200^(0.83 +/- 0.11) while the normalization of the M_200 \propto T_X^{3/2} relation is close to the one expected from hydrodynamical simulations of cluster formation as well as previous X-ray analyses. We suggest that the dispersion in the M_200-T_X and M_200-L_X relations reflects the different merging and dynamical histories for clusters of similar X-ray luminosities and intrinsic variations in their measured masses. Improved statistics of clusters over a wider mass range are required for a better control of the intrinsic scatter in scaling relations.

研究动机与目标

• 利用弱引力透镜方法测量红移z ~ 0.2的X射线明亮星系团样本的总质量和质量分布。
• 利用独立于X射线假设的透镜质量校准集群质量与X射线/光学可观测量之间的标度关系。
• 评估动力学状态和并合历史对质量–温度关系与质量–光度关系中散射的影响。
• 检验观测到的质量–X射线关系与宇宙学模拟预测的一致性。

提出的方法

• 利用加拿大-法国-夏威夷望远镜（CFHT）上的CFH12k相机进行大视场成像的弱引力透镜分析。
• 应用Im2shape软件结合贝叶斯方法测量星系形状并校正PSF展宽效应。
• 通过多波段选择背景星系，实现约每平方弧分10个星系的源密度。
• 在距离星系团中心2 Mpc（15′）范围内以高置信度测量剪切剖面。
• 通过参数化质量模型拟合径向剪切剖面，估算每个星系团的virial质量M_200。
• 将M_200与X射线（L_X, T_X）和光学（L_opt）可观测量进行比较，推导标度关系。

实验结果

研究问题

• RQ1 z ~ 0.2星系团的弱引力透镜质量测量与X射线和光学代理相比如何？
• RQ2 集群质量（M_200）与X射线光度（L_X）之间的标度关系是什么？其与理论预期相比如何？
• RQ3 M_200–T_X关系的归一化值和散射是多少？是否与流体动力学模拟一致？
• RQ4 动力学亚结构和并合历史在质量–可观测量关系散射中起多大作用？

主要发现

• 光学M/L比随集群光度增加而上升，标度关系为M/L ∝ L^{0.80±0.24}，表明更明亮的星系团中暗物质主导性更强。
• L_X–M_200关系的标度为L_X ∝ M_200^{0.83±0.11}，对数斜率显著低于以往研究结果。
• M_200–T_X关系的归一化值为M_200/10^14 M_⊙ = 0.473 h_70^{-1} (T_X/1 keV)^{3/2}，与宇宙学模拟及先前X射线分析结果高度一致。
• M_200–T_X和M_200–L_X关系中的散射较大，且可能源于动力学状态和并合历史的差异，而非测量误差。
• 本研究证实弱引力透镜提供了一种稳健、独立的质量估计算法，由于透镜信号空间范围较大，质量板效应退化程度极低。
• 未来提升弱引力透镜数据质量——尤其是通过深度多波段成像或空间望远镜——将对减小散射并区分物理效应与测量诱导效应至关重要。