Different Methods of Forming Cold Fronts in Nonmerging Clusters
Different Methods of Forming Cold Fronts in Nonmerging Clusters
复制标题
在非合并星团中形成冷锋的不同方法
DOI：
10.1086/522194
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
J. Bregman
中科院分区：
文献类型：
--
作者：
R. Dupke;Raymond E. White III;J. Bregman
X射线表面亮度的锋利边缘和连续的气压在轻松的星系簇（例如Abell 496）中经常发现，例如Abell496。模型将冷界作为当前的子集群合并的生存核心对这些集群的运作不佳，对于这些群集而言，它不太合作，最近提出了涉及气体的竞争模型。在此集群中发现的不连续性与核心合并残余方案不一致。尽管在该簇的冷却半径内发现了整个SN IA铁质量分数的优势，但由硅和铁的丰度确定的沿臂的金属富集与较低的SN IA铁质量分数（51％±14％）一致在周围地区测量的（85％±14％）。发现了这款冷臂，这是当前高分辨率模拟的预测，这是由于中心遇到的，纯净的暗物质halo不太庞大，我们建议A496中的冷锋提供第一个清晰的证实模型，最接近的遭遇发生了〜0.5 Gyr。
Sharp edges in X-ray surface brightness with continuous gas pressure called cold fronts have often been found in relaxed galaxy clusters such as Abell 496. Models that explain cold fronts as surviving cores of head-on subcluster mergers do not work well for these clusters, and competing models involving gas sloshing have been recently proposed. Here, we test some concrete predictions of these models in a combined analysis of density, temperature, metal abundances, and abundance ratios in a deep Chandra exposure of Abell 496. We confirm that the chemical discontinuities found in this cluster are not consistent with a core merger remnant scenario. However, we find chemical gradients across a spiral "arm" discovered at 73 kpc north of the cluster center and coincident with the sharp edge of the main cold front in the cluster. Despite the overall SN Ia iron mass fraction dominance found within the cooling radius of this cluster, the metal enrichment along the arm, determined from silicon and iron abundances, is consistent with a lower SN Ia iron mass fraction (51% ± 14%) than that measured in the surrounding regions (85% ± 14%). The "arm" is also significantly colder than the surroundings by 0.5-1.6 keV. The arm extends from a boxy colder region surrounding the center of the cluster, where two other cold fronts are found. This cold arm is a prediction of current high resolution numerical simulations as a result of an off-center encounter with a less massive pure dark matter halo, and we suggest that the cold fronts in A496 provide the first clear corroboration of such model, where the closest encounter happened ~0.5 Gyr ago. We also argue for a possible candidate dark matter halo responsible for the cold fronts in the outskirts of A496.