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arXiv 1608.01669astro-ph.HEastro-ph.CO
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新发现的早期星系团合并1E2216.0 - 0401和1E2215.7 - 0404的$Suzaku$和$XMM-Newton$观测

$Suzaku$ and $XMM-Newton$ observations of a newly-discovered early-stage cluster merger 1E2216.0-0401 and 1E2215.7-0404

H. Akamatsu, L. Gu, T. W. Shimwell, F. Mernier, J. Mao, I. Urdampilleta, J. de Plaa, H. J. A. Röttgering, J. S. Kaastra

摘要:

我们给出了星团对1E2216.0 - 0401和1E2215.7 - 0404的$Suzaku$和$XMM-Newton$ X射线观测结果。我们发现了星团之间的X射线桥。$Suzaku$和$XMM-Newton$的观测结果表明,每个星系团都有中等温度的气体,分别为$kT_{1E2216.0-0401}=$ 4.8、$\pm$ 0.1 keV和$kT_{1E2215.7-0404}=$ 5.8、$\pm$ 0.2 keV。另一方面,桥区域显示出非常高的温度({\it kT}= 6.6 $\pm$ 0.5 keV)。此外,在桥的位置,我们检测到增强的小波分解的软带(0.5 - 4.0 keV)$XMM-Newton$图像在3西格玛的意义,这是最有可能由于压缩的集群内介质(ICM)的合并活动的结果。这种X射线强度和温度的增强与后期阶段的预期不一致,但与早期阶段合并的数值模拟预测一致。根据桥位置处的温度跃变,马赫数估计为${\cal M}=1.4\pm0.1$,它对应于大约1570 km/s的激波传播速度。根据这些激波的性质,我们估计核通道将发生在0.3 - 0.6Gyr,而激波结构的年龄为50 - 100Myr。基于ICM在桥上的测量特性和时间尺度的估计,我们发现了非平衡电离的迹象。我们还发现可能的弥漫性无线电发射位于合并集群之间。结合射电、X射线和光学图像数据,我们推测探测到的射电源最有可能与合并事件有关。因此,1E2216.0 - 0401和1E2215.7 - 0404是具有显著特征的早期团簇合并的新实例。

英文摘要:

We present the results of $Suzaku$ and $XMM-Newton$ X-ray observations of the cluster pair 1E2216.0-0401 and 1E2215.7-0404. We discover an X-ray bridge between the clusters. $Suzaku$ and $XMM-Newton$ observations revealed that each cluster hosts gas with moderate temperature of $kT_{1E2216.0-0401}=$4.8$\pm$0.1 keV and $kT_{1E2215.7-0404}=$5.8$\pm$0.2 keV, respectively. On the other hand, the bridge region shows a remarkably high temperature ({\it kT}=6.6$\pm$0.5 keV). Furthermore, at the position of the bridge, we detected an enhancement in the wavelet-decomposed soft-band (0.5-4.0 keV) $XMM-Newton$ image at 3 sigma significance, this is most likely due to a compression of the intracluster medium (ICM) as a consequence of the merging activity. This X-ray intensity and temperature enhancement are not consistent with those expected from a late phase, but are in agreement with the predictions by numerical simulations of an early phase merger. From the temperature jump at the location of the bridge, the Mach number is estimated to be ${\cal M}=1.4\pm0.1$, which corresponds to a shock propagation velocity of about 1570 km/s. From the shock properties, we estimate that core-passage will occur in 0.3-0.6 Gyr and that the age of the shock structure is 50--100 Myr. Based on the measured properties of the ICM at the bridge and estimation of timescales, we find indications for non-equilibrium ionization. We also discover possible diffuse radio emission located between the merging clusters. Combining the radio, X-ray, and optical image data, we speculate that the detected radio sources are most likely related to the merger event. Thus, 1E2216.0-0401 and 1E2215.7-0404 is a new example of an early phase cluster merger with remarkable characteristics.

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