后发座星系团中subhalo的朱雀观测
Suzaku observations of subhalos in the Coma cluster
摘要：
我们用{ \it Suzaku}在后发座星系团中观察到了三个巨大的次晕。这些标记为“ID 1”、“ID 2”和“ID 32”的亚晕是使用斯巴鲁/Suprime-Cam进行弱透镜测量检测到的（Okabe等人，2014 a），分别位于距后发座星系团中心1.4 $r_{500}$、1.2 $r_{500}$和1.6 $r_{500}$的投影距离处。次晕“ID 1”在弱透镜质量等值线中心附近有一个紧凑的X射线过量发射，气体质量与弱透镜质量之比约为0.001。发射的温度约为3 keV，略低于周围的团内介质（ICM）和星系团的温度与质量关系的预期。次晕“ID 32”显示了一个过量的发射，其峰值从后发座星系团的中心向相反的方向移动。气体质量与弱透镜质量之比也约为0.001，明显小于常规星系群。超区的温度约为0.5keV，明显低于周围ICM的温度，远离团簇的温度-质量关系。然而，在“ID 2”次晕中没有显著的过量X射线发射。假设在过量X射线发射的边界处，下落速度约为2000 $\rm km~s^{-1}$，“ID 1”和“ID 32”的撞锤压力与单位面积的重力回复力相当。我们还研究了Kelvin-Helmholtz不稳定性对剥离气体的影响。虽然我们发现了与弱透镜暗晕相关的X射线团，但它们的X射线光度远低于星团外围的ICM总光度。
英文摘要：
We observed three massive subhalos in the Coma cluster with {\it Suzaku}. These subhalos, labeled "ID 1", "ID 2", and "ID 32", were detected with a weak-lensing survey using the Subaru/Suprime-Cam (Okabe et al. 2014a), and are located at the projected distances of 1.4 $r_{500}$, 1.2 $r_{500}$, and 1.6 $r_{500}$ from the center of the Coma cluster, respectively. The subhalo "ID 1" has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than that of the surrounding intracluster medium (ICM) and that expected for the temperature vs. mass relation of clusters of galaxies. The subhalo "ID 32" shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature vs. mass relation of clusters. However, there is no significant excess X-ray emission in the "ID 2" subhalo. Assuming an infall velocity of about 2000 $\rm km~s^{-1}$, at the border of the excess X-ray emission, the ram pressures for "ID 1" and "ID 32" are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin-Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.
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