A phenomenological study of star formation and chemical evolution in nearby galaxies
Hughes, Thomas Marcus
arxiv: Astrophysics::Galaxy Astrophysics | Astrophysics::Cosmology and Extragalactic Astrophysics
The main aims of this thesis are: (a) an investigation into the evolutionary histories of nearby galaxies, via the use of ultraviolet-infrared colour-mass diagrams, to uncover the dominant mechanism driving nearby galaxy evolution; (b) the determination of the impact of feedback from active galactic nuclei on star formation; and (c) a study of chemical evolution of star-forming galaxies in different environments. The analysis confirms recent observations of a population of late-type galaxies with reduced levels of star formation. I demonstrate that feedback from active nuclei is unlikely to be the dominant mechanism quenching star formation and driving the evolution of thee late-type galaxies. In fact, galaxies with quenched star formation are typically gas-deficient cluster galaxies, suggesting that environmental effects are responsible for removing the gas required to fuel star formation. A fraction of quenched late-type galaxies are, however, not gas deficient, and form a more heterogeneous class of objects with more complex evolutionary histories. On the other hand, the chemical evolution of star-forming galaxies, as traced by the stellar mass-metallicity relation, is shown to be invariant with environment, suggesting that internal processes drive chemical evolution. The clear observational evidence presented here indicates that, in the concordance model of galaxy formation and evolution, environmental effects must be taken into account in order to gain a better understanding of galaxy evolution in the local universe.