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arXiv 0705.4586astro-ph
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大室女星系团螺旋的磁场

The magnetic fields of large Virgo Cluster spirals

M. Wezgowiec, M. Urbanik, B. Vollmer, R. Beck, K. T. Chyzy, M. Soida, Ch. Balkowski

摘要:

由于它的接近,室女星系团是一个很好的目标,研究星系与星系团环境的相互作用。可以研究高速潮汐相互作用和由团内气体的冲压压力剥离的影响。光学和/或\ion{H}{i}观测并不总是显示星系之间的弱相互作用及其与星系团介质相遇的影响。为此,我们在室女星系团螺旋磁场结构中寻找可能的异常,这些异常可能归因于它们的气体分布和运动学的扰动。五个大角度的室女星系团螺旋星系(NGC 4501、NGC 4438、NGC 4535、NGC 4548和NGC 4654)是使用位于埃费尔斯贝格的100米射电望远镜在4.85千兆赫进行灵敏的总功率和偏振研究的目标。对于两个物体的偏振数据在较高的频率已经获得允许法拉第旋转分析。在所有星系中都发现了扭曲的磁场结构。在NGC 4438(由于核活动)和NGC 4654(潮汐尾和冲压压力效应的组合)中发现了相互作用引起的磁化外流。几乎所有的天体(除了贫血的NGC 4548)都表现出偏振射电连续谱的扭曲,这归因于周围气体的影响。对于一些星系,他们同意其他物种的观测,但有时(NGC 4535)的磁场是与集群环境相互作用的唯一示踪剂。星系团的环境明显地影响了星系的演化,这是由于冲压压力和潮汐效应。磁场为过去的相互作用提供了非常持久的记忆。因此,它们是其他观测难以探测到的弱相互作用的良好示踪剂。

英文摘要:

Because of its proximity the Virgo Cluster is an excellent target for studying interactions of galaxies with the cluster environment. Both the high-velocity tidal interactions and effects of ram pressure stripping by the intracluster gas can be investigated. Optical and/or \ion{H}{i} observations do not always show effects of weak interactions between galaxies and their encounters with the cluster medium. For this reason we searched for possible anomalies in the magnetic field structure in Virgo Cluster spirals which could be attributed to perturbations in their gas distribution and kinematics. Five angularly large Virgo Cluster spiral galaxies (NGC 4501, NGC 4438, NGC 4535, NGC 4548 and NGC 4654) were the targets for a sensitive total power and polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz. For two objects polarization data at higher frequencies have been obtained allowing Faraday rotation analysis. Distorted magnetic field structures were identified in all galaxies. Interaction-induced magnetized outflows were found in NGC 4438 (due to nuclear activity) and NGC 4654 (a combination of tidal tails and ram pressure effects). Almost all objects (except the anaemic NGC 4548) exhibit distortions in polarized radio continuum attributable to influence of the ambient gas. For some galaxies they agree with observations of other species, but sometimes (NGC 4535) the magnetic field is the only tracer of the interaction with the cluster environment. The cluster environment clearly affects the evolution of the galaxies due to ram pressure and tidal effects. Magnetic fields provide a very long-lasting memory of past interactions. Therefore, they are a good tracer of weak interactions which are difficult to detect by other observations.

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