Ages and metallicities of faint red galaxies in the Shapley Supercluster

TL;DR

This study analyzes the stellar populations of 232 faint quiescent galaxies in the Shapley Supercluster, revealing correlations between age, metallicity, and alpha-element abundance across a wide luminosity range.

Contribution

It provides high-precision age and metallicity estimates for low-luminosity galaxies, extending understanding into the faint end of the galaxy population.

Findings

Strong correlation between age and alpha-element abundance.

Anti-correlation of age and metallicity at fixed mass.

Reliable age estimates for faint galaxies with high signal-to-noise data.

Abstract

We present results on the stellar populations of 232 quiescent galaxies in the Shapley Supercluster, based on spectroscopy from the AAOmega spectrograph at the AAT. The key characteristic of this survey is its coverage of many low-luminosity objects (sigma ~ 50 km/s), with high signal-to-noise (~45 per Angstrom). Balmer-line age estimates are recovered with ~25% precision even for the faintest sample members. We summarize the observations and absorption line data, and present correlations of derived ages and metallicities with mass and luminosity. We highlight the strong correlation between age and alpha-element abundance ratio, and the anti-correlation of age and metallicity at fixed mass, which is shown to extend into the low-luminosity regime.