Scaling Properties of Galaxy Groups

TL;DR

Galaxy groups are crucial for understanding cosmic matter evolution, but their study is limited by detection challenges; upcoming surveys will enhance our knowledge of their properties and deviations from theoretical models.

Contribution

This review synthesizes recent observational findings on galaxy group scaling relations and discusses the impact of feedback processes on their properties and deviations from self-similarity.

Findings

Feedback from supernovae and AGNs affects group properties.

Deviations from self-similar scaling are observed and analyzed.

Upcoming surveys will improve detection and understanding of galaxy groups.

Abstract

Galaxy groups and poor clusters are more common than rich clusters, and host the largest fraction of matter content in the Universe. Hence, their studies are key to understand the gravitational and thermal evolution of the bulk of the cosmic matter. Moreover, because of their shallower gravitational potential, galaxy groups are systems where non-gravitational processes (e.g., cooling, AGN feedback, star formation) are expected to have a higher impact on the distribution of baryons, and on the general physical properties, than in more massive objects, inducing systematic departures from the expected scaling relations. Despite their paramount importance from the astrophysical and cosmological point of view, the challenges in their detection have limited the studies of galaxy groups. Upcoming large surveys will change this picture, reassigning to galaxy groups their central role in studying the structure formation and evolution in the Universe, and in measuring the cosmic baryonic content. Here, we review the recent literature on various scaling relations between X-ray and optical properties of these systems, focusing on the observational measurements, and the progress in our understanding of the deviations from the self-similar expectations on groups' scales. We discuss some of the sources of these deviations, and how feedback from supernovae and/or AGNs impacts the general properties and the reconstructed scaling laws. Finally, we discuss future prospects in the study of galaxy groups.