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 ∼4000Å, 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 M_*>10¹⁰M⊙.
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.