From 2013 through to 2017 I was a postgraduate researcher at the Centre for Extragalatic Astronomy at Durham University, working with Professor Alastair Edge.
My research area was the massive galaxies at the centre of clusters of galaxies. These are known as the Brightest Cluster Galaxies or BCGs for short.
This study investigated the prevalence of star formation and AGN activity in BCGs. BCGs are generally assumed to be "red and dead" galaxies, meaning they no longer form new stars at a significant level. However, by searching for BCGs with colours which deviate from the bulk population of galaxies, in a population of ~1000 clusters, we found nearly 14 per cent of these galaxies show detectable levels of activity.
This study aimed to address a selection effect in clusters in which clusters with a strong AGN in the core can go undetected. In shallow X-ray data if an AGN is present the emission is commonly attributed to it, meaning emission from a host cluster may be overlooked. By looking for overdensities in optical telescope data we identified several candidates for rich clusters around X-ray detected AGN and compared photometry of their suspected BCGs with known BCGs of a comparison cluster sample.
This study used integral field spectroscopy to constrain the stellar mass growth of BCGs through galaxy-galaxy mergers. Using MUSE observations we measured the stellar kinematics of 23 cluster cores with apparent close companion galaxies to the BCG and estimated the probability of the companion being bound. Then, by estimating the merger timescales we were able to statistically constrain mass growth rates. A conservative approach gave a nine per cent lower limit and a liberal approach gave an limit of 57 per cent since z=0.25.
This study explored wide-field integral field spectroscopy of ten cluster cores using MUSE. The line intensity ratios are generally found to be consistent with ionisation driven by cooling of the intracluster medium. Two clusters, A2533 and A2566, are found to have optical line emission offset from the BCG and found to be co-spatial with the peak of Chandra X-ray emission. We interpret this as the result of sloshing of the ICM. An ALMA observation of A2533 shows the presence of cold molecular co-spatial with the ionised gas.