SDSS-IV MaNGA: Evidence for enriched accretion onto satellite galaxies
  in dense environments
  We investigate the environmental dependence of the local gas-phase
metallicity in a sample of star-forming galaxies from the MaNGA survey.
Satellite galaxies with stellar masses in the range
$9<\log(M_{*}/M_{\odot})<10$ are found to be $\sim 0.05 \, \mathrm{dex}$ higher
in metallicity than centrals of similar stellar mass. Within the low-mass
satellite population, we find that the interstellar medium (ISM) metallicity
depends most strongly on the stellar mass of the galaxy that is central to the
halo, though there is no obvious difference in the metallicity gradients. At
fixed total stellar mass, the satellites of high mass ($M_{*}>10^{10.5} \,
\mathrm{M_{\odot}}$) centrals are $\sim 0.1 \, \mathrm{dex}$ more metal rich
than satellites of low-mass ($M_{*} < 10^{10} \, \mathrm{M_{\odot}}$) centrals,
controlling for local stellar mass surface density and gas fraction. Fitting a
gas-regulator model to the spaxel data, we are able to account for variations
in the local gas fraction, stellar mass surface density and local escape
velocity-dependent outflows. We find that the best explanation for the
metallicity differences is the variation in the average metallicity of accreted
gas between different environments that depends on the stellar mass of the
dominant galaxies in each halo. This is interpreted as evidence for the
exchange of enriched gas between galaxies in dense environments that is
predicted by recent simulations.
