Nature of Variable and X-ray Selected AGN

Abstract

AGN are one of the most luminous non-transient objects in the universe and have been a subject of study since their discovery in 1943. It has become an up and coming research topic due to the advancements in observation methods and telescope resolution. Owing to these advancements, we are learning more about AGN formation and how it interacts with the environment around it. There are many theories, which are widely accepted, on a probable cause for the formation of the AGN, such as major mergers and other causes of rapid gas inflow. It has also been established that the AGN and its host galaxy interactions can be studied to understand the various theories on formation processes. Studying the host galaxy of the AGN can help in understanding the cause of AGN formation. The host galaxy properties such as stellar mass, star formation rate, magnitude are a part of this thesis. Additionally, the morphological properties, both parametric, such as, Sersic index, and non-parametric like concentration index, asymmetry, Gini index, second order moment of 20% of the galaxy's light (M20) for a sample of 1, 417 host galaxies found both via X-ray emissions and variability selection in the fields covered by CANDELS have been studied. We analyse the morphology of extended AGN host galaxy sources using C-A. G-M20 and log G-log A plots for both methods respectively. These properties for high redshift galaxies are analysed specifically from both the selection methods. We find that the host galaxies in our sample do not display an indication that mergers are dominant in any single analysis method, which rules out major mergers being the primary cause of AGN activation in our sample. Auxiliary visual classification does not indicate disk instabilities being a major cause for AGN formation.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Christopher Conselice (Supervisor) & Gary Fuller (Supervisor)