Gas phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA:
  evidence of metal poor accretion
  We derive the metallicity (traced by the O/H abundance) of the Narrow Line
Region ( NLR) of 108 Seyfert galaxies as well as radial metallicity gradients
along their galaxy disks and of these of a matched control sample of no active
galaxies. In view of that, observational data from the SDSS-IV MaNGA survey and
strong emission-line calibrations taken from the literature were considered.
The metallicity obtained for the NLRs %each Active Galactic Nucleus (AGN) was
compared to the value derived from the extrapolation of the radial oxygen
abundance gradient, obtained from \ion{H}{ii} region estimates along the galaxy
disk, to the central part of the host galaxies. We find that, for most of the
objects ($\sim 80\,\%$), the NLR metallicity is lower than the extrapolated
value, with the average difference ($<D>$) between these estimates ranging from
0.16 to 0.30 dex. We suggest that $<D>$ is due to the accretion of metal-poor
gas to the AGN that feeds the nuclear supermassive black hole (SMBH), which is
drawn from a reservoir molecular and/or neutral hydrogen around the SMBH.
Additionally, we look for correlations between $D$ and the electron density
($N_{\rm e}$), [\ion{O}{iii}]$\lambda$5007 and H$\alpha$ luminosities,
extinction coefficient ($A_{V})$ of the NLRs, as well as the stellar mass
($M_{*}$) of the host galaxies. Evidences of an inverse correlation between the
$D$ and the parameters $N_{\rm e}$, $M_{*}$ and $A_{\rm v}$ were found.
