SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies
  as a function of galaxy mass and type
  We study the internal gradients of stellar population properties within
$1.5\;R_{\rm e}$ for a representative sample of 721 galaxies with stellar
masses ranging between $10^{9}\;M_{\odot}$ to $10^{11.5}\;M_{\odot}$ from the
SDSS-IV MaNGA IFU survey. Through the use of our full spectral fitting code
FIREFLY, we derive light and mass-weighted stellar population properties and
their radial gradients, as well as full star formation and metal enrichment
histories. We also quanfify the impact that different stellar population models
and full spectral fitting routines have on the derived stellar population
properties, and the radial gradient measurements. In our analysis, we find that
age gradients tend to be shallow for both early-type and late-type galaxies.
{\em Mass-weighted} age gradients of early-types are positive ($\sim 0.09\;
{\rm dex}/R_{\rm e}$) pointing to "outside-in" progression of star formation,
while late-type galaxies have negative {\em light-weighted} age gradients
($\sim -0.11\; {\rm dex}/R_{\rm e}$), suggesting an "inside-out" formation of
discs. We detect negative metallicity gradients in both early and late-type
galaxies, but these are significantly steeper in late-types, suggesting that
radial dependence of chemical enrichment processes and the effect of gas inflow
and metal transport are far more pronounced in discs. Metallicity gradients of
both morphological classes correlate with galaxy mass, with negative
metallicity gradients becoming steeper with increasing galaxy mass. The
correlation with mass is stronger for late-type galaxies, with a slope of
$d(\nabla [Z/H])/d(\log M)\sim -0.2\pm 0.05\;$, compared to $d(\nabla
[Z/H])/d(\log M)\sim -0.05\pm 0.05\;$ for early-types. This result suggests
that the merger history plays a relatively small role in shaping metallicity
gradients of galaxies.
