Spatially resolved star formation histories of local post-starburst galaxies: starburst and quenching spatial patterns consistent with recent mergers

Post-starburst (PSB) galaxies, having recently experienced a starburst followed by rapid quenching, are excellent laboratories to probe physical mechanisms that drive starbursts and shutting down of star formation. Integral-field spectroscopy reveals the galaxies’ spatially resolved properties, where observed directional patterns can be linked to the galaxies’ past evolution. We measure the resolved star formation histories, stellar metallicity evolution, and dust properties of three local PSBs from the MaNGA survey, down to 0.5 arcsec resolution (⁠~ 0.3 kpc) using a hierarchical Bayesian model. Local parameters were constrained simultaneously with parameters describing spatial trends. We found that all three galaxies first experienced an outer, weaker, and slower quenching starburst, followed by a central, stronger and faster quenching starburst that peaked ~ 1 Gyr after the first. The central starbursts induced a significantly stronger rise in stellar metallicity compared to the outer starbursts. These results are consistent with the effects of a recent gas-rich (wet) merger, where the first pericentre passage triggered starbursts in the outer regions, while the later coalescence triggers a stronger centralized starburst. We find non-axisymmetric features in the maps of burst mass fraction and dust attenuation in all galaxies, which could be caused by tidal effects during the recent merger. Comparisons with literature binary merger simulations suggest that the galaxies’ rapid quenching was driven by gas consumption and the stabilization against gas gravitational collapse by a growing spheroid, while AGN feedback was not necessarily a primary cause.