The many faces and personalities of galaxies are shaped by physical processes that affect their different components – like bulges and discs – in different ways and leave characteristic imprints on the light and spectra of these components. Disentangling their spectra can reveal vital clues that can be traced back in time to understand how galaxies and their components form and evolve across cosmic time. While individual galaxies give important clues in exquisite detail, a more statistical approach is needed to understand how galaxy populations evolve as a whole. With recent advancements in integral field spectroscopy, which combines both imaging and spectroscopy, we are now equipped with the tools to study the spectra of different regions of galaxies.
This PhD thesis has been part of the BUDDI-MaNGA (Johnston et al. 2022a) collaboration, where we are building the first largest statistical sample of bulge and disc spectra for local galaxies using the 16th and 17th data releases of SDSS-MaNGA. With this novel approach, we examine the spectra of bulges and discs of different types of galaxies – and I focus particularly on spirals. The goals of this project are primarily to look for clues of formation pathways (whether a galaxy forms from the inside-out or from the outside-in) by reconstructing their mass assembly histories and measuring their stellar population parameters. Our results show a clear downsizing effect especially in the bulges, that depends on the component masses – the more massive components assemble earlier and faster than the less massive ones. Additionally, on comparing the stellar populations of the bulges and discs in these galaxies, we find that a majority of the bulges host more metal-rich and older stars than their discs. Our work focuses on identifying these trends in terms of stellar mass and morphology, going from early type spirals to late type spirals (Jegatheesan et al. submitted). A similar study focussing on S0 galaxies in the BUDDI-MaNGA sample was already published in Johnston et al. 2022b. With BUDDI, we also plan to study individual elliptical galaxies with MUSE. Here we consider the possibility that they contain more than one component, each hosting a different stellar population. The higher resolution and field of view of MUSE IFUs allow us to better constrain this and conduct a similar study on the formation pathways and stellar populations of the components of elliptical galaxies. With projects within the BUDDI framework, we aim to look for further hints on the formation and evolution of bulges and discs in today’s galaxy population.
Type of project: PhD thesis
Status: Ongoing
Researchers: KEERTHANA JEGATHEESAN, EVELYN JOANNE JOHNSTON .
Funding source: Becas ANID