Downsizing of galaxies vs upsizing of dark-halos in a Lambda-CDM cosmology

TL;DR

This study uses hydrodynamical simulations within the Lambda-CDM cosmology to explore how smaller galaxies assemble their stellar mass later than larger ones, revealing a downsizing trend influenced by feedback processes.

Contribution

It demonstrates that galaxy stellar mass assembly is inverted relative to dark halo assembly, highlighting the role of feedback in shaping galaxy evolution.

Findings

Dark halos assemble hierarchically.

Smaller galaxies assemble stellar mass later.

Feedback influences the downsizing trend.

Abstract

The mass assembly of a whole population of sub-Milky Way galaxies is studied by means of hydrodynamical simulations within the $\Lambda$-CDM cosmology. Our results show that while dark halos assemble hierarchically, in stellar mass this trend is inverted in the sense that the smaller the galaxy, the later is its stellar mass assembly on average. Our star formation and supernovae feedback implementation in a multi-phase interstellar medium seems to play a key role on this process. However, the obtained downsizing trend is not yet as strong as observations show.