arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1202.5320astro-ph.CO
收藏

合并星系团Abell 2146中的激波阵面、电子-离子平衡和ICM输运过程

Shock fronts, electron-ion equilibration and ICM transport processes in the merging cluster Abell 2146

H. R. Russell, B. R. McNamara, J. S. Sanders, A. C. Fabian, P. E. J. Nulsen, R. E. A. Canning, S. A. Baum, M. Donahue, A. C. Edge, L. J. King, C. P. O'Dea

摘要:

本文报道了对合并星系团Abell 2146的400 ksChandra X射线观测。这一深度观测揭示了与主要合并事件相关的详细结构,包括在致密的冲压压力剥离的子集群核心之前的M=2.3+/-0.2弓形激波,以及ICM中第一个已知的上游激波(M=1.6+/-0.1)。通过测量每个冲击波阵面后面的电子温度分布,我们确定了电子种群与冲击加热离子热平衡的时间尺度。我们发现,弓冲击后面的温度分布是一致的库仑碰撞平衡的时间尺度和postshock温度低于预期的即时冲击加热的电子。虽然像子弹团一样,上游激波阵面后面的电子温度比预期的要热,这有利于瞬时加热模型,但这里温度值的不确定性更大,而且有重要的子结构使解释复杂化。我们还测量了每个激波阵面的宽度和子团核前缘的接触不连续性,以研究ICM中输运过程的抑制。上游激波的长度约为440 kpc,但在这个距离上显得非常窄,与平均自由程23+/-5 kpc相比,最佳拟合宽度仅为6^{+5}_{-3} kpc。子星系团核心的前缘也很窄,宽度上限仅为2 kpc,将0.5-2 keV的冷多相气体与约6 keV的冲击加热ICM分离。这个边缘对扩散和传导的强烈抑制表明,在子星系团核心周围可能形成了一个磁性覆盖层。[删节]

英文摘要:

We present a new 400 ks Chandra X-ray observation of the merging galaxy cluster Abell 2146. This deep observation reveals detailed structure associated with the major merger event including the Mach M=2.3+/-0.2 bow shock ahead of the dense, ram pressure stripped subcluster core and the first known example of an upstream shock in the ICM (M=1.6+/-0.1). By measuring the electron temperature profile behind each shock front, we determine the timescale for the electron population to thermally equilibrate with the shock-heated ions. We find that the temperature profile behind the bow shock is consistent with the timescale for Coulomb collisional equilibration and the postshock temperature is lower than expected for instant shock-heating of the electrons. Although like the Bullet cluster the electron temperatures behind the upstream shock front are hotter than expected, favouring the instant heating model, the uncertainty on the temperature values is greater here and there is significant substructure complicating the interpretation. We also measured the width of each shock front and the contact discontinuity on the leading edge of the subcluster core to investigate the suppression of transport processes in the ICM. The upstream shock is ~440 kpc in length but appears remarkably narrow over this distance with a best-fit width of only 6^{+5}_{-3} kpc compared with the mean free path of 23+/-5 kpc. The leading edge of the subcluster core is also narrow with an upper limit on the width of only 2 kpc separating the cool, multiphase gas at 0.5-2 keV from the shock-heated surrounding ICM at ~6 keV. The strong suppression of diffusion and conduction across this edge suggests a magnetic draping layer may have formed around the subcluster core.[abridged]

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑