Monday

Star-forming galaxies can be transformed into passive systems by a multitude of processes that quench star formation, such as the halting of cold gas accretion (starvation) or the rapid removal of gas in AGN-driven outflows. However, it remains unclear which processes are the most significant, primary drivers of the star-forming–passive bimodality. Leveraging on the statistical power of the SDSS-IV MaNGA galaxy survey, we analyse both the global and spatially-resolved chemical properties of thousands of local star-forming, green valley and passive galaxies to investigate how galaxy quenching depends on mass and environment, and how quenching operates on a radial basis within galaxies. By integrating all the light in each MaNGA galaxy out to 1.5–2.5 Re, we find that the significant difference in the global stellar metallicities of passive galaxies and their star-forming progenitors implies that for galaxies at all masses, quenching must have involved an extended phase of starvation. In order to best match the observed properties of local passive galaxies, some form of gas ejection has to be introduced in our models, with outflows becoming increasingly more important with decreasing stellar mass. Additionally, by dividing each MaNGA galaxy into a series of 0.5 Re-wide annuli, we further find that passive galaxies are in fact substantially more metal-rich than star-forming galaxies at all radii, with the stellar metallicity difference between star-forming and passive galaxies decreasing with increasing radial distance. Therefore, while starvation plays a relatively prominent role in quenching the central regions of galaxies, it plays an increasingly less important role in quenching the outskirts of galaxies, as galactic outflows and gas stripping begin to dominate the quenching process.