The mass-metallicity relation of Lyman-break analogues and its dependence on galaxy properties

TL;DR

This study examines the mass-metallicity relation of local Lyman-break analogues, revealing its dependence on galaxy properties like stellar age and confirming its similarity to high-redshift star-forming galaxies.

Contribution

It demonstrates that galaxy stellar age, indicated by the 4000Å break, influences the mass-metallicity relation and reduces scatter when included as a second parameter.

Findings

Mass-metallicity relation of LBAs matches that of z~1.4-1.7 star-forming galaxies.

Higher 4000Å break correlates with higher metallicity at fixed mass.

Including stellar age reduces scatter in the relation from 0.091 to 0.077 dex.

Abstract

We investigate the mass-metallicity relation and its dependence on galaxy physical properties with a sample of 703 Lyman-break analogues (LBAs) in local Universe, which have similar properties to high redshift star-forming galaxies. The sample is selected according to $\ha$ luminosity, $L(\ha)>10^{41.8}\,{\rm erg\,s^{-1}}$, and surface brightness, $I(\ha)>10^{40.5}\,{\rm erg\,s^{-1}\,kpc^{-2}}$, criteria. The mass-metallicity relation of LBAs harmoniously agrees with that of star-forming galaxies at $z \sim$ 1.4-1.7 in stellar mass range of $10^{8.5}M_{\odot}<M_{*}<10^{11}M_{\odot}$. The relation between stellar mass, metallicity and star formation rate of our sample is roughly consistent with the local fundamental metallicity relation. We find that the mass-metallicity relation shows a strong correlation with the 4000\AA\, break; galaxies with higher 4000\AA\, break typically have higher metallicity at a fixed mass, by 0.06 dex in average. This trend is independent of the methodology of metallicity. We also use the metallicity estimated by $T_{\rm e}$-method to confirm it. The scatter in mass-metallicity relation can be reduced from 0.091 to 0.077 dex by a three-dimensional relation between stellar mass, metallicity and 4000\AA\, break. The reduction of scatter in mass-metallicity relation suggests that the galaxy stellar age plays an important role as the second parameter in the mass-metallicity relation of LBAs.