On the stellar populations of massive galaxies

TL;DR

This paper evaluates semi-analytic galaxy formation models, finding they can replicate old stellar ages but struggle with observed chemical abundances in massive galaxies, indicating fundamental modeling issues.

Contribution

It highlights the limitations of current semi-analytic models in simultaneously matching age and metallicity observations of massive galaxies.

Findings

Models reproduce old stellar populations.

Models fail to match observed chemical abundances.

AGN feedback influences model predictions.

Abstract

In this Letter, we analyse the predicted physical properties of massive galaxies, in the framework of recent semi-analytic models of galaxy formation. All models considered account for winds driven by supernovae explosions and suppression of gas condensation at the centre of relatively massive haloes by active galactic nuclei (AGN). We show that, while these models successfully reproduce the old stellar populations observed for massive galaxies, they fail in reproducing their observed chemical abundances. This problem is alleviate but still present if AGN feedback is completely switched off. Moreover, in this case, model predictions fail in accounting for the old stellar ages of massive galaxies. We argue that the difficulty of semi-analytical models in simultaneously reproducing the observed ages and metallicities of massive galaxies, signals a fundamental problem with the schemes that are currently adopted to model star formation, feedback, and related recycling of gas and metals.