Probing the Evolution of Galaxy Clusters using SZ Effect and Non-thermal Emission
Galaxy clusters are the largest gravitationally bound objects that are stable. They can contain hundreds or even thousands of galaxies, and can weigh as much as 10^15 times the mass of the Sun. About 15% of a cluster’s total mass is made up of the intracluster medium (ICM), while the remaining 5% consists of stars, gas, and dust found within the galaxies themselves. The majority of the cluster’s mass, around 80%, is thought to be made up of dark matter. Cluster mass, along with redshift, can link observations and theory allowing us to derive cosmological constraints from cluster number counts. However, measuring the mass of a cluster is still a challenge. Calibrating mass from ICM observables such as the Sunyaev-Zel’dovich (SZ) effect is subject to uncertainty and biases. The cause of biases and uncertainty is the assumption of hydrostatic equilibrium, while additional non-thermal pressure is not accounted for. On the other hand, merging cluster systems have been shown to exhibit radio emission which implies the presence of non-thermal electrons and a link with disturbances from hydrostatic equilibrium. In this thesis, I present work using a sample of clusters with SZ effect data from the Arcminute Microkelvin Imager and Planck, along with lower-frequency radio data from the Murchison Widefield Array and the LOw Frequency ARray (LOFAR).
Using the SZ effect data, I study deviations of the galaxy cluster gas pressure profile from the average (universal) pressure profile. Meanwhile, with the low-frequency radio data, I investigate the presence and properties of non-thermal radio emission. By comparing the multiwavelength cluster properties, I investigate the connection between thermal and non-thermal electron populations, working toward the ultimate goal of obtaining unbiased and robust estimates of cluster mass.