Abstracts Astronomy & Space Science

A census of stellar structures in the Fornax cluster

by Alan Hung-Shuo Su

<div lang="en" class="abs"><p class="abs_header">Abstract It is well known that galaxies in the Universe tend to be found in either clusters, groups, or in the field, and that the hierarchical growth of structure dictates that galaxies can first aggregate in groups before falling into cluster. The difference in properties between environments (e.g. mass, velocity dispersion, gravitational potential) means that some mechanisms (e.g. ram pressure stripping, harassment, galaxy–cluster tidal interactions) dominate in certain environments. The main aim of this thesis is to study the effects of the environment on the properties of galaxies, particularly between the group and cluster environment, where galaxies can be transformed in groups before entering clusters. To this end, in this thesis I present a detailed view of the stellar structures hosted by galaxies in the Fornax cluster. To study the structures in detail, we use data from the Fornax Deep Survey (FDS), a deep multi-band imaging survey covering 26 deg² around the Fornax cluster. We use the catalogue of likely Fornax members from Venhola et al. (2018) and split the sample into the Fornax main cluster and the Fornax A group. To extract and quantify the stellar structures of galaxies, we conduct structural decompositions with models of varying complexity (single Sérsic, Sérsic+PSF, and multi-component) and calculate non-parametric morphological indices, which provide a global measure of morphology. Additionally, we apply aperture photometry to derive surface brightness profiles in order to study the faint outskirts of galaxies, as well as to measure the integrated and radial colour properties. From the quantities derived from structural decompositions: g − r and r − i colours; effective radius (<em>r_e</em>); Sérsic index (n); mean effective surface brightness (<em>μ_e,r</em>), and non-parametric morphological indices: concentration (C); asymmetry (A); clumpiness (S); Gini (G); brightest second order moment of light (M₂₀), we find significantly (KS test p-value < 0.05) different distributions between galaxies in the Fornax main cluster and the Fornax A group. Specifically, galaxies of a given stellar mass in the Fornax main cluster tend to be redder in g − r, bluer in r − i, larger in re, fainter in <em>μ_e,r</em>, less asymmetric (lower A), and less clumpy (lower S) than their Fornax A group counterparts. Furthermore, we find significant correlations (Spearman’s ρ p-value < 0.05) between the structural quantities and projected cluster-centric distance for the Fornax main cluster galaxies, namely in r − i, <em>r_e</em>, <em>μ_e,r</em>, A, S, G, and M₂₀. This implies that as galaxies fall deeper towards the Fornax main cluster centre, they become bluer in…