SDSS-IV MaNGA: Star Formation Cessation in Low-redshift Galaxies. III. Dependence on Quenching Criteria

Abstract

This paper is the third in a series of studies investigating star formation cessation in nearby galaxies on kiloparsec scales. Using the final SDSS-IV MaNGA data release, we ask how the inferred importance of global, local, and environmental properties depends on the operational definition of quenched regions. We classify spaxels as star-forming, reliably quenched, or potentially quenched by accounting for measurement uncertainties, and train random forest classifiers with a parameter set chosen for direct comparison with previous work. For reliably quenched regions, the local stellar mass surface density $\Sigma_\ast$ consistently has the highest feature importance, independent of quenching definition. By contrast, the high importance of central velocity dispersion $\sigma_c$, previously interpreted as evidence for galaxy-wide AGN feedback, is recovered mainly when potentially quenched regions are included. The leading parameter also varies with stellar mass: $\Sigma_{\rm 1kpc}$ is most important below $\sim10^{10.2}\,\textrm{M}_{\odot}$, whereas local quantities such as $\Sigma_\ast$ and $\sigma_\ast$ become more prominent at high masses. These results show that quenching criteria and uncertainty treatment can reconcile apparently discrepant feature-importance studies. AGN-related processes may contribute to ambiguous regions, but the reliably quenched population is most tightly linked to high local stellar density.