Abundance gradients in low surface brightness spirals: clues on the origin of common gradients in galactic discs

TL;DR

This study reveals that low surface brightness galaxies (LSBGs) commonly exhibit metallicity gradients, which are generally shallower than those in high surface brightness galaxies, suggesting a universal relation influenced by surface mass density.

Contribution

The paper demonstrates that metallicity gradients are prevalent in LSBGs and are comparable to HSBGs when normalized by disc scale length, challenging previous beliefs of their absence.

Findings

Metallicity gradients are common in LSBGs.

LSBG gradients are shallower than in HSBGs when measured in isophotal radius.

LSBGs share similar gradients with HSBGs when normalized by disc scale length.

Abstract

We acquired spectra of 141 HII regions in ten late-type low surface brightness galaxies (LSBGs). The analysis of the chemical abundances obtained from the nebular emission lines shows that metallicity gradients are a common feature of LSBGs, contrary to previous claims concerning the absence of such gradients in this class of galaxies. The average slope, when expressed in units of the isophotal radius, is found to be significantly shallower in comparison to galaxies of high surface brightness. This result can be attributed to the reduced surface brightness range measured across their discs, when combined with a universal surface mass density-metallicity relation. With a similar argument we explain the common abundance gradient observed in high surface brightness galaxy (HSBG) discs and its approximate dispersion. This conclusion is reinforced by our result that LSBGs share the same common abundance gradient with HSBGs, when the slope is expressed in terms of the exponential disc scale length.