GASP and MaNGA surveys shed light on the enigma of the gas metallicity
  gradients in disk galaxies
  Making use of both MUSE observations of 85 galaxies from the survey GASP (GAs
Stripping Phenomena in galaxies with MUSE) and a large sample from MaNGA
(Mapping Nearby Galaxies at Apache Point Observatory survey) we investigate the
distribution of gas metallicity gradients as a function of stellar mass, for
local cluster and field galaxies. Overall, metallicity profiles steepen with
increasing stellar mass up to $10^{10.3}\,{\rm M_\odot}$ and flatten out at
higher masses. Combining the results from the metallicity profiles and the
stellar mass surface density gradients, we propose that the observed steepening
is a consequence of local metal enrichment due to in-situ star formation during
the inside-out formation of disk galaxies. The metallicity gradient-stellar
mass relation is characterized by a rather large scatter, especially for
$10^{9.8}<{\rm M_\star/M_\odot}<10^{10.5}$, and we demonstrate that metallicity
gradients anti-correlate with the galaxy gas fraction. Focusing on the galaxy
environment, at any given stellar mass, cluster galaxies have systematically
flatter metallicity profiles than their field counterparts. Many
sub-populations coexist in clusters: galaxies with shallower metallicity
profiles appear to have fallen into their present host halo sooner and have
experienced the environmental effects for a longer time than cluster galaxies
with steeper metallicity profiles. Recent galaxy infallers, like galaxies
currently undergoing ram-pressure stripping, show metallicity gradients more
similar to those of field galaxies, suggesting they have not felt the effect of
the cluster yet.
