Semi-analytic galaxy formation in f(R)-gravity cosmologies

TL;DR

This study uses high-resolution simulations and semi-analytic models to explore how f(R)-gravity affects galaxy formation and structure growth, finding subtle differences from standard cosmology.

Contribution

It introduces a combined simulation and semi-analytic approach to predict galaxy properties in f(R)-gravity cosmologies, accounting for modified virial scaling.

Findings

Dark matter haloes have higher velocity dispersion at fixed mass in f(R)-gravity.

Galaxy properties like stellar mass function are very similar to LCDM predictions.

Linear growth rate of cosmic structures is altered in f(R)-gravity, detectable via large galaxy surveys.

Abstract

Modifications of the equations of general relativity at large distances offer one possibility to explain the observed properties of our Universe without invoking a cosmological constant. Numerous proposals for such modified gravity cosmologies exist, but often their consequences for structure formation in the non-linear sector are not yet accurately known. In this work, we employ high-resolution numerical simulations of f(R)-gravity models coupled with a semi-analytic model (SAM) for galaxy formation to obtain detailed predictions for the evolution of galaxy properties. The f(R)-gravity models imply the existence of a `fifth-force', which is however locally suppressed, preserving the successes of general relativity on solar system scales. We show that dark matter haloes in f(R)-gravity models are characterized by a modified virial scaling with respect to the LCDM scenario, reflecting a higher dark matter velocity dispersion at a given mass. This effect is taken into account in the SAM by an appropriate modification of the mass--temperature relation. We find that the statistical properties predicted for galaxies (such as the stellar mass function and the cosmic star formation rate) in f(R)-gravity show generally only very small differences relative to LCDM, smaller than the dispersion between the results of different SAM models, which can be viewed as a measure of their systematic uncertainty. We also demonstrate that galaxy bias is not able to disentangle between f(R)-gravity and the standard cosmological scenario. However, f(R)-gravity imprints modifications in the linear growth rate of cosmic structures at large scale, which can be recovered from the statistical properties of large galaxy samples.