Properties of the outer regions of spiral disks: abundances, colors and   ages
  We summarize the results obtained from our suite of chemical evolution models for spiral disks, computed for different total masses and star formation efficiencies. Once the gas, stars and star formation radial distributions are reproduced, we analyze the Oxygen abundances radial profiles for gas and stars, in addition to stellar averaged ages and global metallicity. We examine scenarios for the potential origin of the apparent flattening of abundance gradients in the outskirts of disk galaxies, in particular the role of molecular gas formation prescriptions. 
Mercedes Moll\'a, Angeles I. D\'iaz, Brad K. Gibson, Oscar Cavichia,   and \'Angel-R. L\'opez-S\'anchez
astro-ph.GA