The CALIFA Survey: Exploring the Oxygen Abundance in the Local Universe

Abstract

We present here a review of the latest results on the spatially-resolved analysis of the stellar populations and ionized gas of disk-dominated galaxies based on Calar Alto Legacy Integral Field Area (CALIFA) data. CALIFA is an ongoing integral field spectroscopy (IFS) survey of galaxies in the Local Universe (0.005 < z < 0.03) that has already obtained spectroscopic information up to ∼2.5 re with a spatial resolution better than ∼1 kpc for a total number of more than 600 galaxies of different morphological types, covering the color-magnitude diagram up to MR<−18 mag. With nearly 2000 spectra obtained for each galaxy, CALIFA offers one of the best IFU datasets to study the star formation histories and chemical enrichment of galaxies. In this article, we focus on the main results from the analysis of the oxygen abundances based on the study of ionized gas in H II regions and individual spaxels and their relation to the global properties of galaxies, using an updated/revised dataset with more galaxies and ionized regions. In summary, we have confirmed previous published results indicating that: (1) the M-Z relation does not present a secondary relation to the star formation rate, when the abundance is measured at the effective radius; (2) the oxygen abundance presents a strong correlation with the stellar surface density (∑-Z relation); (3) the oxygen abundance profiles present three well-defined regimes: (i) an overall negative radial gradient between 0.5 and 2 re, with a characteristic slope of αO/H ∼−0.1 dex/re; (ii) a universal flattening beyond >2 re; and (iii) an inner drop at <0.5 re that depends on mass; (4) the presence of bending in the surface brightness profile of disk galaxies is not clearly related to either the change in the shape of the oxygen abundance profile or the properties of the underlying stellar population. All of these results indicate that disk galaxies present an overall inside-out growth, with chemical enrichment and stellar mass growth tightly correlated and dominated by local processes and limited effects of radial mixing or global outflows. However, clear deviations are shown with respect to this simple scenario, which affect the abundance profiles in both the innermost and outermost regions of galaxies