The baryonic mass assembly of low-mass halos in a Lambda-CDM Universe

TL;DR

This study investigates the assembly histories of dark, gas, and stellar mass in low-mass halos within a Lambda-CDM universe, revealing stable gas-to-baryon ratios and the evolution of intrahalo gas properties over cosmic time.

Contribution

It provides new insights into the baryonic mass assembly and gas dynamics in low-mass halos, highlighting the role of intrahalo gas and feedback processes.

Findings

Gas-to-baryon fraction remains relatively constant over time.

Most baryons are in intrahalo gas rather than galaxies.

Intrahalo gas temperature and phase vary with halo mass and redshift.

Abstract

We analyse the dark, gas, and stellar mass assembly histories of low-mass halos (Mvir ~ 10^10.3 - 10^12.3 M_sun) identified at redshift z = 0 in cosmological numerical simulations. Our results indicate that for halos in a given present-day mass bin, the gas-to-baryon fraction inside the virial radius does not evolve significantly with time, ranging from ~0.8 for smaller halos to ~0.5 for the largest ones. Most of the baryons are located actually not in the galaxies but in the intrahalo gas; for the more massive halos, the intrahalo gas-to-galaxy mass ratio is approximately the same at all redshifts, z, but for the least massive halos, it strongly increases with z. The intrahalo gas in the former halos gets hotter with time, being dominant at z = 0, while in the latter halos, it is mostly cold at all epochs. The multiphase ISM and thermal feedback models in our simulations work in the direction of delaying the stellar mass growth of low-mass galaxies.