A multiwavelength study of active galactic nuclei in clusters of galaxies
Abstract
Clusters of galaxies offer a unique laboratory for studying the effects of environment on the properties of Active Galactic Nuclei (AGN), and conversely, the feedback effects of AGN on their environment. Recent observations of cluster cores reveal cavities in the X-ray emission of the intracluster medium (ICM). With obvious signs of altering the gas properties of the ICM, cluster AGN can be used to investigate feedback mechanisms in dense cluster environments. This thesis incorporates multiwavelength observations of clusters of galaxies to identify radio galaxies and X-ray points sources (XPSs) within 1 Mpc of the cluster center and presents a first look at the evolution of these objects in a consistent manner. Guided by the results of cosmological simulations, 23 clusters of galaxies between 0.2<z<1.2 are selected because their bulk ICM temperatures are consistent with Coma Cluster progenitors at the cluster redshift. In 0.2<z<0.4 clusters, we detect 20 radio galaxies at P1.4GHz ≥ 3x1023 W Hz-1 and 8 XPSs at L0.3-8.0 keV >1042 erg s-1. Except for one XPS, the cluster radio galaxies and XPSs are hosted by passive galaxies that are more centrally concentrated than their parent population. We suggest that cluster XPSs are low-luminosity BL Lac objects, similar in nature to the radio galaxies. We estimate that all L>L* cluster red sequence galaxies are radio-loud and possess jets. We suggest that >50% of the lower-power radio sources below our detection limits supply the majority of the heat to the ICM. The radio luminosity function of cluster radio galaxies reveals number and luminosity evolution in Coma Cluster progenitors from 0.4<z<1.2 to 0.2<z<0.4, and little evolution from 0.2<z<0.4 to z=0. Seventy-five percent of those cluster radio galaxies are still located within 500 kpc where they can deposit heat via AGN jets near the cluster core. Seven spectroscopically confirmed cluster XPSs provide evidence for a higher X-ray active fraction at 0.4<z<1.2 than at 0.2<z<0.4, similar to the trend detected for the cluster radio galaxies. The increased cluster AGN numbers and luminosity detected in high-z Coma-like clusters suggests a larger input of heat to the ICM when the clusters were forming compared to their heat input at the current epoch.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- November 2010
- Bibcode:
- 2010PhDT........89H
- Keywords:
-
- Physics, Astrophysics