揭示星系团的三维结构：解决X射线和透镜质量之间的差异
Unveiling the three-dimensional structure of galaxy clusters: resolving the discrepancy between X-ray and lensing masses
摘要：
首次测定了三轴星系团中暗物质和团内介质的三维形状和物理参数。虽然大多数以前的研究依赖于标准的球形建模，我们的方法允许推断的非球形的集群内的气体分布坐在三轴DM晕内的流体静力学平衡相结合的X射线，弱和强透镜观测的属性。我们提出了我们的方法的应用程序的星系团MACS J1423.8+2404。这个源是一个很好的放松对象的一个单峰质量分布的例子，我们推断的ICM和DM的形状和物理性质，这个源。我们发现这是一个三轴星系团，在天空平面上和沿视线方向，DM晕轴比分别为1.53+/-0.15和1.44+/-0.07。我们表明，占的三维几何形状可以解决长期存在的星系团质量之间的差异确定从X射线和引力透镜观测。我们还专注于确定DM密度分布α的内部斜率，因为暗物质密度分布的尖度是冷暗物质（CDM）结构形成范例的关键测试之一：我们通过明确考虑该簇的3D结构来测量α =0.94+/-0.09，该值接近CDM预测，而标准球面建模导致偏置值α =1.24+/-0.07。我们的发现为CDM方案提供了进一步的证据，并为无偏差地恢复星系团的内在形状和物理参数打开了一扇新的窗口。这在使用星系团作为宇宙学探测器时有重要的意义。
英文摘要：
[Abridged] We present the first determination of the intrinsic three-dimensional shapes and the physical parameters of both dark matter (DM) and intra-cluster medium (ICM) in a triaxial galaxy cluster. While most previous studies rely on the standard spherical modeling, our approach allows to infer the properties of the non-spherical intra-cluster gas distribution sitting in hydrostatic equilibrium within triaxial DM halos by combining X-ray, weak and strong lensing observations. We present an application of our method to the galaxy cluster MACS J1423.8+2404. This source is an example of a well relaxed object with a unimodal mass distribution and we infer shape and physical properties of the ICM and the DM for this source. We found that this is a triaxial galaxy cluster with DM halo axial ratios 1.53+/-0.15 and 1.44+/-0.07 on the plane of the sky and along the line of sight, respectively. We show that accounting for the three-dimensional geometry allows to solve the long-standing discrepancy between galaxy cluster masses determined from X-ray and gravitational lensing observations. We focus also on the determination of the inner slope of the DM density profile alpha, since the cuspiness of dark-matter density profiles is one of the critical tests of the cold dark matter (CDM) paradigm for structure formation: we measure alpha=0.94+/-0.09 by accounting explicitly for the 3D structure for this cluster, a value which is close to the CDM predictions, while the standard spherical modeling leads to the biased value alpha=1.24+/-0.07. Our findings provide further evidences that support the CDM scenario and open a new window in recovering the intrinsic shapes and physical parameters of galaxy clusters in a bias-free way. This has important consequences in using galaxy clusters as cosmological probes.
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