标题： 松散群星系中的HI含量 显示英文标题

标题： HI content in galaxies in loose groups

摘要： 众所周知，星团中的螺旋星系存在气体缺乏现象，并且认为冲击气压剥离是主要的气体去除机制。在一些致密星团中也报告了气体缺乏的现象。然而，松散星团中的气体缺乏尚未得到充分证实。小而松散的星团中成员速度的分散度较低，以及星团内介质密度较低，有利于潮汐剥离作为它们的主要气体去除过程。最近来自Parkes全天HI巡天（HIPASS）数据和附近带有相关弥散X射线辐射的松散星团目录的发布使我们能够检验这一观点。 本文旨在探讨以下问题：(a) 具有弥散X射线辐射的星团中的星系是否统计上比没有弥散X射线辐射的星团中的星系具有更低的气体含量？(b) HI缺乏程度是否系统地随着松散星团的X射线亮度的变化而变化？ 我们的研究发现：(a) 具有弥散X射线辐射的星团中的星系平均来说HI缺乏，与没有X射线辐射的星团中的星系相比，已经失去了更多的气体；后者被发现不存在显著的HI缺乏；(b) 没有发现HI缺乏程度与X射线亮度之间存在系统性依赖关系。可以解释这种过度气体损失的两种可能机制是冲击压力辅助的潮汐剥离和热传导蒸发。 显示英文摘要

摘要： Gas deficiency in cluster spirals is well known and ram-pressure stripping is considered the main gas removal mechanism. In some compact groups too gas deficiency is reported. However, gas deficiency in loose groups is not yet well established. Lower dispersion of the member velocities and the lower density of the intra-group medium in small loose groups favour tidal stripping as the main gas removal process in them. Recent releases of data from HI Parkes all sky survey (HIPASS) and catalogues of nearby loose groups with associated diffuse X-ray emission have allowed us to test this notion. In this paper, we address the following questions: (a) do galaxies in groups with diffuse X-ray emission statistically have lower gas content compared to the ones in groups without diffuse X-ray emission? (b) does HI deficiency vary with the X-ray luminosity of the loose group in a systematic way? We find that (a) galaxies in groups with diffuse X-ray emission, on average, are HI deficient, and have lost more gas compared to those in groups without X-ray emission; the later are found not to have significant HI deficiency; (b) no systematic dependence of the HI deficiency with X-ray luminosity is found. Ram pressure assisted tidal stripping and evaporation by thermal conduction are the two possible mechanisms to account for this excess gas loss.