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 r e 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 M R < −18 mag. With nearly 2000 spectra obtained for each galaxy, CALIFA offers one of the best IFUdatasets to study the star Galaxies 2015, 3 165 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 (Σ-Z relation); (3) the oxygen abundance profiles present three well-defined regimes: (i) an overall negative radial gradient between 0.5 and 2 r e , with a characteristic slope of α O/H ∼−0.1 dex/r e ; (ii) a universal flattening beyond >2 r e ; and (iii) an inner drop at <0.5 r e 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.

Separate Ways: The Mass–Metallicity Relation Does Not Strongly Correlate with Star Formation Rate in SDSS-IV MaNGA Galaxies

“…Sánchez et al (2013) could not confirm this secondary relation using integral field spectroscopic data covering the full optical extension of the galaxies, extracted from the CALIFA dataset (Sánchez et al 2012). This result was confirmed recently with more statistics by Sánchez et al (2015b). In a recent study using drift-scan integrated spectra, Hughes et al (2013) show that a secondary relation of the MZR with the SFR is not present.…”

Oxygen abundance maps of CALIFA galaxies

“…[N ii]λ6584/Hα vs. [O iii]λ5007/Hβ diagram seems to be the most stringent condition to select true H ii regions (Vogt et al 2014). However, an appreciable fraction of H ii regions is located to the right (thus on the "wrong" side) of this demarcation line (Sánchez et al 2015b). The goal of the current study is to construct metallicity maps of galaxies.…”

“…The intensities of the strong lines can be used to separate different types of emission-line objects according to their main excitation mechanism. Baldwin et al (1981) Kewley et al 2001;Kauffmann et al 2003;Stasińska et al 2006;Singh et al 2013;Vogt et al 2014;Belfiore et al 2015;Sánchez et al 2015b). The exact location of the dividing line between H ii regions and AGNs is still under debate.…”

“…They concluded that most of this scatter can be attributed to random errors and is not caused by an intrinsic dispersion. Sánchez et al (2015b) selected and investigated 396 H ii regions in the galaxy NGC 6754. They found evidence of an azimuthal variation in the oxygen abundance of about 0.05 dex, which may be related to radial migration.…”

Isolated Galaxies versus Interacting Pairs with MaNGA

“…Uncertainties come from the observed spectra (noise and calibration of the data), from synthesis models, and from the limitations of the spectral synthesis method [14]. Moreover, the information extracted from the multi stellar population modelling differs among implementations [15]. Since we present here a pilot study and some improvements will be implemented in modelling and full spectral fitting, we leave the analysis of the uncertainties for the future work.…”