SDSS-IV MaNGA: The Roles of AGNs and Dynamical Processes in Star
  Formation Quenching in Nearby Disk Galaxies
  We study how star formation (SF) is quenched in low-redshift disk galaxies
with integral-field spectroscopy. We select 131 face-on spiral galaxies with
stellar mass greater than $\rm 3\times10^{10}M_\odot$, and with spatially
resolved spectrum from MaNGA DR13. We subdivide the sample into four groups
based on the offset of their global specific star formation rate (SFR) from the
star-forming main sequence and stack the radial profiles of stellar mass and
SFR. By comparing the stacked profiles of quiescent and star-forming disk
galaxies, we find that the decrease of the global SFR is caused by the
suppression of SF at all radii, but with a more significant drop from the
center to the outer regions following an inside-out pattern. As the global
specific SFR decreases, the central stellar mass, the fraction of disk galaxies
hosting stellar bars, and active galactic nuclei (AGNs; including both LINERs
and Seyferts) all increase, indicating dynamical processes and AGN feedback are
possible contributors to the inside-out quenching of SF in the local universe.
However, if we include only Seyferts, or AGNs with ${\rm EW(H\alpha)>3\AA}$,
the increasing trend of AGN fraction with decreasing global sSFR disappears.
Therefore, if AGN feedback is contributing to quenching, we suspect that it
operates in the low-luminosity AGN mode, as indicated by the increasing large
bulge mass of the more passive disk galaxies.
