XRISM国际合作小组报道了半人马座星系团核心气体的大量运动。这一研究成果发表在2025年2月12日出版的国际学术期刊《自然》上。

据悉，星系温度计含有大量的热电离气体，称为温度计介质（ICM）。在松弛的磁芯中，ICM的辐射冷却时间比磁芯的年龄短。然而，与冷却相关的线发射的缺失表明，加热机制抵消了冷却，来自活动星系核（AGN）的反馈最有可能是最微弱的。湍流和大块运动，如地核气体在低温电势井中的振荡（晃动）运动，也被认为是地核外部热分布的机制。

课题组展示了用x射线成像和光谱任务卫星，对半人马座星系进行的x射线光谱观测。研究小组发现，相对于中央星系，热气体沿着视线流动，速度从130公里/秒至310公里/秒，在中心的大约30kpc以内。这表明大量流动与岩心气体晃动一致。尽管大量流动可以防止中心冷却气体的过度积聚，但它可以分散AGN注入的热量，并从周围的ICM中引入热能。研究发现气体的速度弥散仅为120公里/秒，甚至在AGN的大约10kpc以内。这表明AGN对周围ICM运动的影响是有限的。

附：英文原文

Title: The bulk motion of gas in the core of the Centaurus galaxy cluster

Author: Yutaka Fujita or Kosuke Sato.

Issue&Volume: 2025-02-12

Abstract: Galaxy clusters contain vast amounts of hot ionized gas known as the intracluster medium (ICM). In relaxed cluster cores, the radiative cooling time of the ICM is shorter than the age of the cluster. However, the absence of line emission associated with cooling suggests heating mechanisms that offset the cooling, with feedback from active galactic nuclei (AGNs) being the most likely source1,2. Turbulence and bulk motions, such as the oscillating (‘sloshing’) motion of the core gas in the cluster potential well, have also been proposed as mechanisms for heat distribution from the outside of the core3,4. Here we present X-ray spectroscopic observations of the Centaurus galaxy cluster with the X-Ray Imaging and Spectroscopy Mission satellite. We find that the hot gas flows along the line of sight relative to the central galaxy, with velocities from 130kms1 to 310kms1 within about 30kpc of the centre. This indicates bulk flow consistent with core gas sloshing. Although the bulk flow may prevent excessive accumulation of cooled gas at the centre, it could distribute the heat injected by the AGN and bring in thermal energy from the surrounding ICM. The velocity dispersion of the gas is found to be only 120kms1 in the core, even within about 10kpc of the AGN. This suggests that the influence of the AGN on the surrounding ICM motion is limited in the cluster.

DOI: 10.1038/s41586-024-08561-z

Source: https://www.nature.com/articles/s41586-024-08561-z