The soft X-ray emission in a large sample of galaxy clusters with ROSAT PSPC
The soft X-ray emission in a large sample of galaxy clusters with ROSAT PSPC
复制标题
使用 ROSAT PSPC 观测大型星系团样本中的软 X 射线发射
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
J. Nevalainen
中科院分区：
文献类型：
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作者：
M. Bonamente;R. Lieu;M. Joy;J. Nevalainen
对ROSAT PSPC观测到的38个x射线选择星系团的软x射线发射研究表明，软过量现象可能是星系团中常见的现象。超过星团内热介质贡献的过量软x射线辐射在很大一部分源中是明显的，并且在最深的观测中被清楚地探测到，具有很大的统计显著性。这项调查依赖于新的高分辨率21厘米HI观测。样品选择还包括对红外图像的分析，以进一步确保结果与银河系吸收特性相关的可靠性。本底效应或校准效应作为过量辐射原因的可能性也进行了同样的研究；对过量发射的分布与探测器位置和银河系HI柱密度的详细分析表明，过量发射是一种真实的天体现象。我们发现，在距离星团中心大于~150 ~ 200kpc的距离处，软多余辐射有优先分布的证据；这种行为可以在非热逆康普顿情景中自然解释。或者，我们提出这种现象可能是由最近的流体动力学模拟中看到的非常大规模的“热”细丝的热发射引起的。这种新的解释减轻了传统的簇内“热”气体和非热气体的苛刻要求。我们还研究了来自未解析的x射线微弱星系团的软过量的可能性。
The study of soft X-ray emission of 38 X-ray selected galaxy clusters observed by ROSAT PSPC indicates that the soft excess phenomenon may be a common occurrence in galaxy clusters. Excess soft X-ray radiation, above the contribution from the hot intra-cluster medium, is evident in a large fraction of sources, and is clearly detected with large statistical significance in the deepest observations. The investigation relies on new, high resolution 21 cm HI observations. The sample selection also features analysis of infra-red images, to further ensure reliability of results with respect to the characteristics of Galactic absorption. The possibility of background or calibration effects as cause of the excess emission is likewise investigated; a detailed analysis of the distribution of the excess emission with respect to detector position and Galactic HI column density shows that the excess emission is a genuine celestial phenomenon. We find evidence for a preferential distribution of the soft excess emission at distances larger than ~150-200 kpc from the centers of clusters; this behavior may be naturally explained in the context of a non-thermal Inverse-Compton scenario. Alternatively, we propose that the phenomenon may be caused by thermal emission of very large-scale `warm' filaments seen in recent hydrodynamic simulations. This new interpretation relieves the very demanding requirements of either the traditional intra-cluster `warm' gas and the non-thermal scenarios. We also investigate the possibility of the soft excess originating from unresolved, X-ray faint cluster galaxies.