SDSS-IV MaNGA: Spatially resolved star-formation histories and the
  connection to galaxy physical properties
  A key task of observational extragalactic astronomy is to determine where --
within galaxies of diverse masses and morphologies -- stellar mass growth
occurs, how it depends on galaxy properties and what processes regulate star
formation. Using spectroscopic indices derived from the stellar continuum at
$\sim 4000$\AA, we determine the spatially resolved star-formation histories of
980000 spaxels in 2404 galaxies in the SDSS-IV MaNGA IFU survey. We examine the
spatial distribution of star-forming, quiescent, green valley, starburst and
post-starburst spaxels as a function of stellar mass and morphology to see
where and in what types of galaxy star formation is occurring. The spatial
distribution of star-formation is dependent primarily on stellar mass, with a
noticeable change in the distribution at \mstar$>10^{10}$\msun. Galaxies above
this mass have an increasing fraction of regions that are forming stars with
increasing radius, whereas lower mass galaxies have a constant fraction of star
forming regions with radius. Our findings support a picture of inside-out
growth and quenching at high masses. We find that morphology (measured via
concentration) correlates with the fraction of star-forming spaxels, but not
with their radial distribution. We find (post-)starburst regions are more
common outside of the galaxy centre, are preferentially found in asymmetric
galaxies, and have lower gas-phase metallicity than other regions, consistent
with interactions triggering starbursts and driving low metallicity gas into
regions at $<1.5R_e$.
