并合星系团热气中铁的丰度分布
Iron abundance distribution in the hot gas of merging galaxy clusters
摘要：
利用XMM-Newton/EPIC方法对6个正在合并的星系团进行了观测，研究了它们的温度、铁丰度和赝熵沿合并轴的分布.这是第一次，我们集中在同时，并在一个全面的方式，对化学和热力学性质的新鲜碰撞的群内介质（ICM）。这些集群沿合并轴的Fe分布被发现是在良好的协议与典型的非冷芯集群的方位平均Fe丰度分布到$r_{500}$。除了显示出中等的中心丰度峰（尽管不如松弛系统中明显）之外，Fe丰度在大半径处接近$\sim$ 0.2-0.3 $Z_\odot$。虽然这种浅的金属分布是符合的想法，干扰，非冷核心集群起源于合并的放松，冷核心集群，我们发现，在某些情况下，残留的金属丰富和低熵冷核心可以坚持后，主要合并。虽然我们在（较低熵，$K$ = 200-500 keV cm $^2$）内部区域中获得Fe丰度和伪熵之间的温和反相关性，但在（较高熵，$K$ = 500-2300 keV cm $^2$）外部半径处没有发现明显的相关性。我们在大半径处发现的明显的空间丰度均匀性很难通过新注入金属的有效混合来解释，特别是在合并后的时间很短的系统中。相反，我们的研究结果提供了重要的额外证据，支持早期富集的情况-其中大部分金属在$z$ > 2-3时释放到星系外-并将其从冷核和（中等）非冷核星系团扩展到一些最受干扰的合并星系团。这些结果构成了第一步，更深入地了解合并集群的化学史。
英文摘要：
We present XMM-Newton/EPIC observations of six merging galaxy clusters and study the distributions of their temperature, iron (Fe) abundance and pseudo-entropy along the merging axis. For the first time, we focus simultaneously, and in a comprehensive way, on the chemical and thermodynamic properties of the freshly collided intracluster medium (ICM). The Fe distribution of these clusters along the merging axis is found to be in good agreement with the azimuthally-averaged Fe abundance profile in typical non-cool-core clusters out to $r_{500}$. In addition to showing a moderate central abundance peak, though less pronounced than in relaxed systems, the Fe abundance flattens at large radii towards $\sim$0.2-0.3 $Z_\odot$. Although this shallow metal distribution is in line with the idea that disturbed, non-cool-core clusters originate from the merging of relaxed, cool-core clusters, we find that in some cases, remnants of metal-rich and low entropy cool cores can persist after major mergers. While we obtain a mild anti-correlation between the Fe abundance and the pseudo-entropy in the (lower entropy, $K$ = 200-500 keV cm$^2$) inner regions, no clear correlation is found at (higher entropy, $K$ = 500-2300 keV cm$^2$) outer radii. The apparent spatial abundance uniformity that we find at large radii is difficult to explain through an efficient mixing of freshly injected metals, particularly in systems for which the time since the merger is short. Instead, our results provide important additional evidence in favour of the early enrichment scenario - in which the bulk of the metals are released outside galaxies at $z$ > 2-3 - and extend it from cool-core and (moderate) non-cool-core clusters to a few of the most disturbed merging clusters as well. These results constitute a first step towards a deeper understanding of the chemical history of merging clusters.
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