Modelling galaxy clustering: Is new physics needed in galaxy formation models?

TL;DR

This paper evaluates galaxy formation models against observed galaxy clustering data, identifying discrepancies due to satellite galaxy overproduction, and shows that including satellite mergers and tidal dissolution improves model accuracy.

Contribution

It introduces simple models for satellite mergers and tidal dissolution, demonstrating their necessity for aligning galaxy clustering predictions with observations.

Findings

Models qualitatively match data but lack quantitative accuracy.

Overproduction of satellite galaxies causes discrepancies.

Including satellite mergers and tidal dissolution improves model fit.

Abstract

The clustering amplitude of galaxies depends on their intrinsic luminosity. We compare the properties of publicly available galaxy formation models with clustering measurements from the two-degree field galaxy redshift survey. The model predictions show the same qualitative behaviour as the data but fail to match the observations at the level of accuracy at which current measurements can be made. We demonstrate that this is due to the model producing too many satellite galaxies in massive haloes. We implement simple models to describe two new processes, satellite-satellite mergers and the tidal dissolution of satellites to investigate their impact on the predicted clustering. We find that both processes need to be included in order to produce a model which matches the observations.