Galactic Hubs: New Insights and SKA View of AGN Feedback in Galaxy Groups

Abstract

Over the last two decades, significant effort has been devoted to understand the physical processes involved in galaxy evolution. In this context, AGN feedback has emerged as the leading explanation for several longstanding astrophysical questions, including the origin of scaling relations between supermassive black holes and their host galaxies. Galaxy clusters have been particularly put under the lens, thanks to the combination of high-resolution X-ray and radio observations which allowed to investigate the link between thermal and non-thermal emission. On the other hand, research in the lower-mass regime of galaxy groups remains limited. This is mostly due to observational limitations in the high-energy regime, which prevents the study of the non-thermal emission in the context of its surrounding environment. Nevertheless, this is a key topic for galaxy evolution, as the vast majority of radio-loud AGN in the nearby Universe are hosted in galaxy groups. Recently, modern radio facilities such as LOFAR, uGMRT and MeerKAT have obtained interesting results in this regime. Examples include signatures of overheating caused by AGN, groups with largely evacuated environments due to powerful and prolonged feedback activity, and remnant plasma displaced by large-scale sloshing motions. This chapter reviews these advances while identifying gaps in our understanding. We will explore how SKA promises to close these gaps and revolutionise the field through its unparalleled combination of high resolution and sensitivity across a wide frequency range. Moreover, its unique capabilities, in synergy with state-of-the-art and upcoming surveys carried out by new instruments, will facilitate the construction of unprecedentedly large samples of groups, dramatically enhancing the statistical power of future studies.