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arXiv 2008.01299astro-ph.GAastro-ph.HE
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基于Chandra X射线图像的964个星系团的动力学状态

Dynamical state for 964 galaxy clusters from Chandra X-ray images

Z. S. Yuan, J. L. Han

AI总结:

本研究利用Chandra X射线图像对964个星系团计算动力学参数,提出形态指数δ以描述动力学状态,并验证其与射电功率和质量平面的关联。

摘要:

星系团的动力学状态描述了星系团是处于动力学弛豫状态还是子团并合过程中。利用钱德拉X射线天文台的档案图像,我们推导出一组参数来描述964个星系团的动力学状态。在半径为500千秒差距的圆形中心区域内,计算了三个广泛使用的动力学状态指标:浓度指数c、质心偏移ω和功率比P3/P0。我们还在最佳拟合的椭圆区域内推导了两个自适应参数:轮廓参数κ和不对称因子α。然后通过结合这两个自适应参数定义了形态指数δ,该指数指示了星系团的动力学状态,并与浓度指数c、质心偏移ω、功率比P3/P0以及光学弛豫因子Γ具有良好的相关性。对于大样本星系团,动力学参数从扰动状态到弛豫状态连续分布,峰值位于两者之间,而非两种状态的双峰分布。我们发现新推导的形态指数δ适用于具有弥散射电巨晕和迷你晕的星系团在射电功率、星系团质量与动力学状态之间的相似基本平面。从苏尼亚耶夫-泽尔多维奇效应和X射线图像估计的质量之间的偏移依赖于动力学参数。从钱德拉档案图像推导出的所有星系团动力学参数可在http://zmtt.bao.ac.cn/galaxy_clusters/dyXimages/获取。

英文摘要:

The dynamical state of galaxy clusters describes if clusters are relaxed dynamically or in a merging process of subclusters. By using archival images from the Chandra X-ray Observatory, we derive a set of parameters to describe the dynamical state for 964 galaxy clusters. Three widely used indicators for dynamical state, the concentration index c, the centroid shift omega and the power ratio P3/P0 are calculated in the circular central region with a radius of 500 kpc. We also derive two adaptive parameters, the profile parameter kappa and the asymmetry factor alpha, in the best fitted elliptical region. The morphology index delta is then defined by combining these two adaptive parameters, which indicates the dynamical state of galaxy clusters and has good correlations to the concentration index c, the centroid shift omega, the power ratio P3/P0, and the optical relaxation factor Gamma. For a large sample of clusters, the dynamical parameters are continuously distributed from the disturbed to relaxed states with a peak in the between, rather than the bimodal distribution for the two states. We find that the newly derived morphology index delta works for the similar fundamental plane between the radio power, cluster mass and the dynamical state for clusters with diffuse radio giant-halos and mini-halos. The offset between masses estimated from the Sunyaev-Zeldovich effect and X-ray images depends on dynamical parameters. All dynamical parameters for galaxy clusters derived from the Chandra archival images are available on http://zmtt.bao.ac.cn/galaxy_clusters/dyXimages/.

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