Dwarf galaxy populations in present-day galaxy clusters: I. Abundances and red fractions

TL;DR

This study compares observed dwarf galaxy populations in major galaxy clusters with a semi-analytic model, revealing good overall agreement but also highlighting discrepancies in red fractions and dwarf-to-giant ratios, suggesting areas for model improvement.

Contribution

The paper provides a detailed comparison between observed dwarf galaxy populations and a semi-analytic model across multiple clusters, identifying specific successes and shortcomings of the model.

Findings

Model reproduces dwarf galaxy density profiles well.

Red fractions match observations in Coma and Perseus but not in Virgo.

Dwarf-to-giant ratio in the model is higher than observed.

Abstract

We compare the galaxy population in the Virgo, Fornax, Coma and Perseus cluster to a state-of-the-art semi-analytic model, focusing on the regime of dwarf galaxies with luminosities from approximately 10^8 L_sun to 10^9 L_sun. We find that the number density profiles of dwarfs in observed clusters are reproduced reasonably well, and that the red fractions of model clusters provide a good match to Coma and Perseus. On the other hand, the red fraction among dwarf galaxies in Virgo is clearly lower than in model clusters. We argue that this is mainly caused by the treatment of environmental effects in the model. This explanation is supported by our finding that the colours of central ("field") dwarf galaxies are reproduced well, in contrast to previous claims. Finally, we find that the dwarf-to-giant ratio in model clusters is too high. This may indicate that the current model prescription for tidal disruption of faint galaxies is still not efficient enough.