Raj, Maria Angela (2020) The fate of late-type galaxies in the Fornax cluster, mapped with deep imaging data. [Tesi di dottorato]

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The main objective of the work presented in this thesis is to study the bright ($m_B < 16$ mag) late-type galaxies (LTGs) in the Fornax cluster core and compare their structure and relevant properties (e.g. stellar mass, $g-i$ colours) to those in the Fornax~A subgroup. In this thesis, I present the surface photometry of 22 LTGs in the Fornax cluster i.e. 13 in the core and nine in the subgroup, observed with the Fornax Deep Survey (FDS). With the multi-band ($u$, $g$, $r$, $i$) and deep images of FDS, I investigate the faint outskirts of the LTGs and estimate the amount of intra-group light (IGL). Since the Fornax cluster is observed in multiple wavelengths, I use some ancillary data to discuss the individual LTGs and trace their evolutionary path in the cluster. The main results of this work suggest that the dense environment of the cluster core inhibits the formation of spiral galaxies and therefore, the very late-type galaxies with morphological type $5 < T \leq 9$ are located beyond the high-density ($> 0.8$ deg) regions of the Fornax cluster. From the analysis of the break-radius and break type, six out of nine LTGs in the Fornax A group are of Type-III, which is either suggestive of strangulation halting the star-formation in their outer discs or a consequence of H\textsc{i}-richness, while the cluster core LTGs have Type-II and Type-III profiles. In the Fornax~A group, the absence of morphology and colour segregation of LTGs with group-centric distance, and the low IGL fraction (16\%) suggest that the evolutionary phase of the group is different from that of the cluster core. This is further supported by the effect of the environment on the structure of LTGs, where we find that the break-radius of most ($\sim$ 80\%) of the cluster core LTGs are located within 1$R_e$, contrary to those in the group ($>1R_e$). By comparing the aforementioned properties and analysing them in projected phase-space, I discuss `pre-processing' of galaxies before cluster infall thereby providing clues to the hierarchical merging of groups into the main cluster. During the merging of groups, the IGL mixes with the intra-cluster light thus forming the bulk of the intra-cluster baryons inside the core of the Fornax cluster. All of the mentioned work not only helps us to understand the evolution of LTGs in the Fornax cluster but also provides clues to their structure-transformation in other dense clusters. Finally, by comparing observational results to those from simulations, I predict the fate of LTGs in the Fornax cluster.

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