X-ray Properties of Galaxy Groups and Clusters

Abstract

Active Galactic Nuclei (AGN) plays an important role in the evolution of large scale structure in the universe. A large number of observations, ranging from X-ray studies of galaxy clusters to observing correlations between the central supermassive black hole (SMBH) with their host galaxies, point to its important role in structure formation. In this thesis, we explore the influence of feedback from AGN on their surrounding medium and study the cosmological evolution of AGN along with their host dark matter halos and galaxies. For this purpose, we use a cosmological volume simulation that includes dark matter dynamics, hydrodynamics, star formation along with a subgrid modeling of black hole formation and their associated feedback (Di Matteo et al. 2008; Khandai et al. 2015). We investigate various correlated properties of AGN-host galaxies and explain them in terms of feedback from the AGN. From the temperature and density maps of the gas surrounding the central SMBH, we statistically show that AGN feedback effectively evacuates the gas in the ambient medium as well as energize them, resulting in a deficit of the cold gas supply, which in turn suppresses the black hole growth and halts star formation. Moreover, we model the theoretical X-ray emission from galaxy groups and clusters and develop a promising technique of synthetic X-ray observation to compare the theoretical results with actual observations. We find that the stacked X-ray emission from the diffuse gas surrounding the black holes in the presence and absence of AGN feedback reveals a suppression in the X-ray surface brightness profile in the vicinity of the AGN producing feedback. This also shows agreement with the results from real observations. Finally, we aim to establish the robustness of our simulated results by comparing them with the results of a different cosmological simulation (Dav´e et al. 2019, SIMBA). We show that galaxy, black hole and X-ray properties of individual systems in both the simulations agree well with each other, indicating their ubiquity. We further show that different modes of feedback might have substantially – 6 – different effect on the galaxy and gas properties for AGN host galaxies. Finally, we propose new observations with current and upcoming X-ray telescopes to investigate the effect of AGN feedback in galaxies and clusters in the high redshift universe.