X-ray analysis of the galaxy group UGC 03957 beyond R200 with Suzaku
X-ray analysis of the galaxy group UGC 03957 beyond R200 with Suzaku
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DOI：
10.1051/0004-6361/201527608
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发表时间：
2016-03
影响因子：
6.5
通讯作者：
Sophia Thölken;L. Lovisari;L. Lovisari;T. Reiprich;J. Hasenbusch
中科院分区：
文献类型：
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作者：
Sophia Thölken;L. Lovisari;L. Lovisari;T. Reiprich;J. Hasenbusch
上下文。在过去的几年里，人们对星系团的外围进行了详细的研究，这些分析带来了一些有趣的结果，比如可能的气体聚集和流体静力、热和电离平衡的破坏。这些现象会影响聚类的熵分布，通常在r200左右表现出与自相似预测的偏差。然而，对于星系群来说，仍然存在重大的不确定性。特别是熵分布是否与星系团相似的问题。目标。利用Suzaku卫星在四个方位上研究了1.4 R 200≈1.4 Mpc的星系群UGC 03957的气体性质。我们检查了方位对称性，并获得了温度、熵、密度和气体质量剖面。先前的研究指出，在群和簇的外围偏离平衡状态，因此我们研究了这些大半径处气体的流体动力学状态。方法。我们对UGC 03957的5个Suzaku观测数据和5个Chandra快照观测数据进行了光谱分析，这些观测数据的曝光时间总计约为138 ks。我们研究了不同背景分量中的点扩散函数和不确定性等系统效应，并对密度和温度剖面进行了去投影。结果。我们发现从中心到外围的温度下降了约3倍，这与先前对星系团的结果一致。金属丰度剖面显示出沿大半径的平坦行为，这暗示了星系风是主要的ICM富集过程。在进行气体质量分数校正后，熵分布与数值模拟基本一致。反馈过程和AGN活动可能是熵修正的一种解释，在星系团中，熵修正的半径比在星系团中更大。先前对簇和群的分析通常显示熵在~ r200附近趋于平缓甚至下降，这可能是外围聚集或非平衡状态的指示。这种熵行为在UGC 03957中是不存在的。气体质量分数远低于宇宙平均值，但在r200以上上升，这可能是在这些大半径处偏离流体静力平衡的暗示。通过测量中间半径处α元素Si和S的丰度，我们确定了不同类型超新星的相对数量，并发现丰度模式可以用核心坍缩超新星的相对贡献80% ~ 100%来描述。这一结果与之前对星系群的测量结果一致。
Context. In the last few years, the outskirts of galaxy clusters have been studied in detail and the analyses have brought up interesting results such as indications of possible gas clumping and the breakdown of hydrostatic, thermal, and ionization equilibrium. These phenomena affect the entropy profiles of clusters, which often show deviations from the self-similar prediction around R 200 . However, significant uncertainties remain for groups of galaxies. In particular the question, of whether entropy profiles are similar to those of galaxy clusters. Aims. We investigated the gas properties of the galaxy group UGC 03957 up to 1.4 R 200 ≈ 1.4 Mpc in four azimuthal directions with the Suzaku satellite. We checked for azimuthal symmetry and obtained temperature, entropy, density, and gas mass profiles. Previous studies point to deviations from equilibrium states at the outskirts of groups and clusters and so we studied the hydrodynamical status of the gas at these large radii. Methods. We performed a spectral analysis of five Suzaku observations of UGC 03957 with ~138 ks good exposure time in total and five Chandra snapshot observations for point source detection. We investigated systematic effects such as point spread function and uncertainties in the different background components, and performed a deprojection of the density and temperature profile. Results. We found a temperature drop of a factor of ~3 from the center to the outskirts that is consistent with previous results for galaxy clusters. The metal abundance profile shows a flat behavior towards large radii, which is a hint for galactic winds as the primary ICM enrichment process. The entropy profile is consistent with numerical simulations after applying a gas mass fraction correction. Feedback processes and AGN activity might be one explanation for entropy modification, imprinting out to larger radii in galaxy groups than in galaxy clusters. Previous analyses for clusters and groups often showed an entropy flattening or even a drop around ~ R 200 , which can be an indication of clumping or non-equilibrium states in the outskirts. Such entropy behavior is absent in UGC 03957. The gas mass fraction is well below the cosmic mean but rises above this value beyond R 200 , which could be a hint for deviations from hydrostatic equilibrium at these large radii. By measuring the abundance of the α -elements Si and S at intermediate radii we determined the relative number of different supernovae types and found that the abundance pattern can be described by a relative contribution of 80%−100% of core-collapse supernovae. This result is in agreement with previous measurements for galaxy groups.