Somewhere in between: Tracing the Radio Emission from Galaxy Groups (or Why Does the Future of Observing Galaxy Groups with Radio Telescopes Look Promising?)

Błażej Nikiel-Wroczyński

doi:10.3390/galaxies9040084

Abstract

Galaxy groups constitute the most common class of galaxy systems in the known Universe, unique in terms of environmental properties. However, despite recent advances in optical and infrared observations as well as in theoretical research, little is known about magnetic fields and the associated continuum radio emission. Studies on this issue have only been conducted in recent years, and many questions have yet to be resolved. This article aims to put the study of group magnetism in a broader context, to present recent advances in the field (mainly achieved with low-frequency radio interferometers), and to list the issues that need to be addressed in future observations. To make it easier for the Readers to get acquainted with the concepts presented in the manuscript, radio observations of two sample groups of galaxies are also presented.

Highlights

Galaxy Groups as a Very Special Class of ObjectsGalaxies in the Universe live either in solitude or in interacting systems
In order to provide example imaging material demonstrating the quality of the data one can obtain using the low-frequency infrastructure, two galaxy groups have been chosen: HCG 15, and HCG 60
Do we find radio emission in most of them, or are there any systems with no detection, even at the lowest radio frequencies? How old are the radio haloes in fossils? Metrewave data should make it possible to look at the remnants of processes that ceased more than a hundred Myrs ago

Summary

Introduction

Galaxies in the Universe live either in solitude or in interacting systems. Taffy galaxies—systems of interacting spirals, one detected by Condon et al [2], another one by Condon et al [3]—are a much better illustration of what a pair of galaxies looks like. Both of these systems contain member galaxies, and a wide, magnetised intergalactic bridge. Such structures are among the main drivers of studies on interacting systems

Objectives

Methods

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Conclusion