The diverse quenching pathways of post-starburst galaxies in SDSS-IV MaNGA

ABSTRACT The quenching of star formation in galaxies is an important aspect of galaxy evolution, but the physical mechanisms that drive it are still not understood. Measuring the spatial distribution of quenching can help determine these mechanisms. We present the star formation histories (SFHs) and stellar metallicity evolution of rapidly quenched regions in 86 local post-starburst (PSB) galaxies from the Mapping Nearby Galaxies at APO (MaNGA) integral field survey, obtained through Bayesian full spectral fitting of their rest-frame optical spectra. We found that regardless of spatial location, the PSB regions have similar past SFHs and chemical evolution, once radial metallicity gradients are accounted for. This suggests that all PSB regions are regulated by a common set of local scale processes in the interstellar medium, regardless of the broader triggering mechanism. We show that the centres of galaxies with outer PSB regions are also quenching. The central specific star formation rate has declined by ${\sim} 1.0$ dex on average during the last 2 Gyr, a significantly steeper decline than main sequence galaxies over the same period (${\approx} 0.2$ dex). This central quenching can be either synchronous, outside-in or inside-out, and slower or as fast as the outer regions, highlighting the diversity of quenching pathways for local galaxies. Our results imply a primary quenching mechanism that is both catastrophic and global in rapidly halting star formation in local galaxies. We suggest the predominant cause is galaxy mergers or interactions, with large scale feedback from a starburst or a central supermassive black hole playing a lesser role.