Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

Abstract

We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3−4 disc effective radii (r e ). We confirm the results obtained from classical H  region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 r e of α O/H = − 0.075 dex/r e with a scatter of σ = 0.016 dex/r e when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude, and the presence or absence of bars. In particular, barred galaxies do not seem to display shallower gradients, as predicted by numerical simulations. Interestingly, we find that most of the galaxies in the sample with reliable oxygen abundance values beyond ∼2 effective radii (57 galaxies) present a flattening of the abundance gradient in these outer regions. This flattening is not associated with any morphological feature, which suggests that it is a common property of disc galaxies. Finally, we detect a drop or truncation of the abundance in the inner regions of 27 galaxies in the sample; this is only visible for the most massive galaxies.

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

“…In Fig. 1 we demonstrate this fact by comparing our sample of galaxies with a well-defined sample presented in a previous work of the oxygen abundance radial distribution (Sánchez-Menguiano et al 2016b, hereafter SM16) based on the CALIFA survey (Calar Alto Legacy Integral Field Area Survey, Sánchez et al 2012a). We should note that the comparison sample was extracted from a well defined, statistically significant sample and representative of galaxies in the Local Universe (Walcher et al 2014).…”

“…However, recently it has been found that some spiral galaxies show lower (higher) oxygen abundance val-ues in the inner (outer) regions than that expected according to the observed negative gradients. This results in a nearly flat distribution or even a drop towards the centre (Belley & Roy 1992;Rosales-Ortega et al 2011;Sánchez et al 2012bSánchez et al , 2014Sánchez-Menguiano et al 2016b;Zinchenko et al 2016), and an abundance flattening or even an increase in the outermost parts (Martin & Roy 1995;Vilchez & Esteban 1996;Roy & Walsh 1997;van Zee et al 1998;Rosales-Ortega et al 2011;Bresolin et al 2012;Marino et al 2012;López-Sánchez et al 2015;Sánchez-Menguiano et al 2016b;Belfiore et al 2017).…”

“…Peimbert 1979;Shaver et al 1983;Vila-Costas & Edmunds 1992;Zaritsky et al 1994;Kennicutt et al 2003;Pilyugin et al 2004;Bresolin et al 2009b;Rosales-Ortega et al 2011;Marino et al 2012;Sánchez et al 2012b;Pilyugin et al 2014;Sánchez et al 2014;Sánchez-Menguiano et al 2016b;Zinchenko et al 2016;Belfiore et al 2017). However, recently it has been found that some spiral galaxies show lower (higher) oxygen abundance val-ues in the inner (outer) regions than that expected according to the observed negative gradients.…”

“…The first IFS studies that analysed statistically the properties of the H ii regions were presented by the PINGS project (Rosales-Ortega et al 2010), with the disadvantage of being limited to a dozen nearby galaxies. The use of these techniques on 'survey mode', that offers the opportunity to carry out these studies on large samples of galaxies, was crucial to reach meaningful statistical results (Moustakas et al 2010;Rich et al 2012;Sánchez et al 2012bSánchez et al , 2014Ho et al 2015;Sánchez-Menguiano et al 2016b;Zinchenko et al 2016;Belfiore et al 2017).…”

“…Ho et al (2015), based on the use of simple chemical evolution models, proposed that this common gradient was the result of common gas and stellar surface density profiles under the co-evolution of gas, stars, and metals during the mass growth of disc galaxies. IFS surveys have also allowed us to find a relation between the inner abundance drop presented in spiral galaxies and the galaxy mass, being this feature more common in more massive galaxies (Sánchez-Menguiano et al 2016b). Regarding the study of azimuthal abundance variations in spiral galaxies, Zinchenko et al (2016) suggested that there is no significant global azimuthal asymmetry in the oxygen abundance distribution, establishing a limit of ∼ 0.05 dex for these asymmetries, although works analysing in detail individual galaxies indicate otherwise (Sánchez-Menguiano et al 2016a;Vogt et al 2017).…”