Sparse Reconstruction of the Merging A520 Cluster System
Sparse Reconstruction of the Merging A520 Cluster System
复制标题
合并A520集群系统的稀疏重构
DOI：
10.3847/1538-4357/aa850d
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Jean
中科院分区：
文献类型：
--
作者：
A. Peel;F. Lanusse;Jean
合并的星系团为研究天体物理学背景下的暗物质特性提供了独特的机会。这些是罕见且极端的宇宙事件，其中大部分重子物质从碰撞子星团的暗物质晕中移位。由于所有质量都会使光弯曲，因此弱引力透镜是研究此类系统中总质量分布的主要工具。结合X射线和光学分析，根据弱透镜观测重建的星团合并质量图已被用来约束暗物质的自相互作用横截面。动态复杂的 Abell 520 (A520) 星团是一个特例，即使在合并系统中也是如此：多波长观测揭示了暗质量令人惊讶的高质光浓度，在有效无碰撞暗物质的标准假设下很难对其进行解释。我们使用一种新的基于稀疏性的质量映射算法重新审视 A520，以独立评估令人费解的暗核的存在。我们从哈勃太空望远镜对该系统的观测得出的两个独立的星系形状目录获得了高分辨率质量重建。我们的质量图总体上与之前的研究结果一致，但我们发现了重要的差异。特别是，尽管我们能够在两个数据集中识别出一定水平的暗核，但其重要性比使用相同数据之前报告的要低得多。由于我们无法在分析中确认检测结果，因此我们不认为 A520 对无碰撞暗物质场景构成重大挑战。
Merging galaxy clusters present a unique opportunity to study the properties of dark matter in an astrophysical context. These are rare and extreme cosmic events in which the bulk of the baryonic matter becomes displaced from the dark matter halos of the colliding subclusters. Since all mass bends light, weak gravitational lensing is a primary tool to study the total mass distribution in such systems. Combined with X-ray and optical analyses, mass maps of cluster mergers reconstructed from weak-lensing observations have been used to constrain the self-interaction cross-section of dark matter. The dynamically complex Abell 520 (A520) cluster is an exceptional case, even among merging systems: multi-wavelength observations have revealed a surprising high mass-to-light concentration of dark mass, the interpretation of which is difficult under the standard assumption of effectively collisionless dark matter. We revisit A520 using a new sparsity-based mass-mapping algorithm to independently assess the presence of the puzzling dark core. We obtain high-resolution mass reconstructions from two separate galaxy shape catalogs derived from Hubble Space Telescope observations of the system. Our mass maps agree well overall with the results of previous studies, but we find important differences. In particular, although we are able to identify the dark core at a certain level in both data sets, it is at much lower significance than has been reported before using the same data. As we cannot confirm the detection in our analysis, we do not consider A520 as posing a significant challenge to the collisionless dark matter scenario.