Bar effect on gas-phase abundance gradients. II. Luminosity-dependent flattening

TL;DR

This study investigates how the presence of bars in spiral galaxies affects the radial distribution of gas-phase metallicities, revealing that luminosity influences the impact of bars on abundance gradients, with implications for galaxy evolution.

Contribution

It demonstrates that the bar effect on metallicity gradients depends on galaxy luminosity, clarifying previous conflicting results and highlighting the role of bars in disc evolution.

Findings

Barred galaxies have shallower abundance gradients across luminosities.

Unbarred galaxies show steeper gradients at lower luminosities.

Luminosity influences the detectability of the bar effect on metallicity profiles.

Abstract

We present here the second part of a project that aims at solving the controversy on the issue of the bar effect on the radial distribution of metals in the gas-phase of spiral galaxies. In Paper I we presented a compilation of more than 2800 HII regions belonging to 51 nearby galaxies for which we derived chemical abundances and radial abundance profiles from a homogeneous methodology. In this paper we analyse the derived gas-phase radial abundance profiles of 12+log(O/H) and log(N/O), for barred and unbarred galaxies separately, and find that the differences in slope between barred and unbarred galaxies depend on galaxy luminosity. This is due to a different dependence of the abundance gradients (in dex/kpc) on luminosity for the two types of galaxies: In the galaxy sample that we consider the gradients appear to be considerably shallower for strongly barred galaxies in the whole luminosity range, while profile slopes for unbarred galaxies become steeper with decreasing luminosity. Therefore, we only detect differences in slope for the lower luminosity (lower mass) galaxies (M_B >~ -19.5 or M_* <~ 10^{10.4} M_sun). We discuss the results in terms of the disc evolution and radial mixing induced by bars and spiral arms. Our results reconcile previous discrepant findings that were biased by the luminosity (mass) distribution of the sample galaxies and possibly by the abundance diagnostics employed.