Gas-phase metallicity profiles of the Bluedisk galaxies: Is metallicity
  in a local star-formation regulated equilibrium?
  As part of the Bluedisk survey we analyse the radial gas-phase metallicity
profiles of 50 late-type galaxies We compare the metallicity profiles of a
sample of HI-rich galaxies against a control sample of HI-'normal' galaxies. We
find the metallicity gradient of a galaxy to be strongly correlated with its HI
mass fraction (M(HI) / Mstar). We note that some galaxies exhibit a steeper
metallicity profile in the outer disc than in the inner disc. These galaxies
are found in both the HI-rich and control samples. This contradicts a previous
indication that these outer drops are exclusive to HI-rich galaxies. These
effects are not driven by bars, although we do find some indication that barred
galaxies have flatter metallicity profiles. By applying a simple analytical
model we are able to account for the variety of metallicity profiles that the
two samples present. The success of this model implies that the metallicity in
these isolated galaxies may be in a local equilibrium, regulated by star
formation. This insight could provide an explanation of the observed local
mass-metallicity relation.
