2015AJ....150..192Z

The factors that influence the chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce the gas-phase abundance of heavy elements (metallicity), whereas ongoing star formation continuously increases it. To exclude the stellar nucleosynthesis from consideration, we analyze for a sample of 14 spiral galaxies the radial distribution of the effective yield of oxygen y_eff, which would be identical to the true stellar yield (per stellar generation) y_o if the evolution followed the closed-box model. As the initial data for gas-phase abundance, we used the O/H radial profiles from Moustakas et al., based on two different calibrations (the PT2005 and KK2004 methods). In most of the galaxies with the PT2005 calibration, which we consider the preferred one, the yield y_effin the main disk (R ≥ 0.2 R₂₅ where R₂₅is the optical radius) increases with radius, remaining lower than the empirically found true stellar yield y_o. This may indicate the inflow of less-enriched gas predominantly to the inner disk regions, which reduces y_eff. We show that the maximal values of the effective yield in the main disks of galaxies, y_eff, max_ anticorrelate with the total mass of galaxies and with the mass of their dark halos enclosed within R₂₅. It allows us to propose the greater role of gas accretion for galaxies with massive halos. We also found that the radial gradient of oxygen abundance normalized to R₂₅ has a tendency to be shallower in the systems with lower dark halo to stellar mass ratio within the optical radius, which, if confirmed, gives evidence of the effective radial mixing of gas in galaxies with a relatively light dark matter halo.