Resolving the signatures of the environmental quenching of star formation with SAMI

In this thesis we use spatially resolved spectroscopy from the SAMI Galaxy Survey to investigate the mechanisms that suppress, or quench, the star formation (SF) in galaxies in dense environments. We calculate integrated star formation rate (SFR) and quantify the distribution of SF in different ways, including the radial distribution of SF and the non-parametric r50,Hα/r50,cont. These measurements are compared to various environment density metrics from the GAMA survey. The spatial signatures of environment quenching vary with the stellar mass of the galaxies. Massive galaxies in dense environments are quenched outside-in, while low mass galaxies do not appear to exhibit such behaviour. We find that the signatures of environment quenching are most likely to be seen in galaxy groups more massive than 1012.5 M⊙. Above this halo mass the fraction of galaxies that appear to be environmentally affected rises significantly. Within groups there is no correlation between the indicators of environment quenching and other measures of environment. From the projected phase-space distribution of the quenching galaxies in the groups, we speculate that the changes in the SF properties of these galaxies must occur over timescales longer than the group dynamical time. Using a case study of 4 galaxies with centrally-concentrated SF and a mass-matched control sample, we study how the gradients in the stellar populations of galaxies change during quenching. We derive stellar population age profiles and find that the quenching galaxies are 0.7 ± 0.6 Gyr older at Re than the controls. Based on their residence in massive groups and their star-formation morphology, we suggest that the outer parts of these galaxies have been quenched by an event that rapidly stripped the gas in their discs, leaving the inner parts of the galaxy to quench by starvation