On the mass assembly of low-mass galaxies in hydrodynamical simulations of structure formation

TL;DR

This study uses cosmological hydrodynamical simulations to analyze the mass assembly and evolution of low-mass galaxies, comparing results with observations within the Lambda-CDM framework.

Contribution

It provides new insights into the mass assembly trends of low-mass galaxies and evaluates the impact of supernova feedback in simulations against observational data.

Findings

Smaller galaxies have higher specific star formation rates and gas fractions.

Simulated stellar mass fractions increase with halo mass, aligning with semi-empirical models.

At high redshift, simulated galaxy properties are broadly consistent with observations.

Abstract

Cosmological hydrodynamical simulations are studied in order to analyse generic trends for the stellar, baryonic and halo mass assembly of low-mass galaxies (M_* < 3 x 10^10 M_sun) as a function of their present halo mass, in the context of the Lambda-CDM scenario and common subgrid physics schemes. We obtain that smaller galaxies exhibit higher specific star formation rates and higher gas fractions. Although these trends are in rough agreement with observations, the absolute values of these quantities tend to be lower than observed ones since z~2. The simulated galaxy stellar mass fraction increases with halo mass, consistently with semi-empirical inferences. However, the predicted correlation between them shows negligible variations up to high z, while these inferences seem to indicate some evolution. The hot gas mass in z=0 halos is higher than the central galaxy mass by a factor of ~1-1.5 and this factor increases up to ~5-7 at z~2 for the smallest galaxies. The stellar, baryonic and halo evolutionary tracks of simulated galaxies show that smaller galaxies tend to delay their baryonic and stellar mass assembly with respect to the halo one. The Supernova feedback treatment included in this model plays a key role on this behaviour albeit the trend is still weaker than the one inferred from observations. At z>2, the overall properties of simulated galaxies are not in large disagreement with those derived from observations.