# The history of the dark and luminous side of Milky Way-like progenitors

## TL;DR

This study models the evolution of Milky Way-like galaxies from early cosmic times to the present, predicting properties of their progenitors and analyzing the roles of different halo types in galaxy formation and reionization.

## Contribution

It applies a novel simulation approach to trace MW progenitors from high redshift, revealing the significance of mini-halos and dynamical effects in galaxy evolution and reionization.

## Key findings

- MW progenitors follow observed relations up to z=4
- Mini-halos contribute significantly to early star formation
- Dynamical effects redistribute baryonic matter at low redshift

## Abstract

Here we investigate the evolution of a Milky Way (MW) -like galaxy with the aim of predicting the properties of its progenitors all the way from $z \sim 20$ to $z = 0$. We apply GAMESH (Graziani et al. 2015) to a high resolution N-Body simulation following the formation of a MW-type halo and we investigate its properties at $z \sim 0$ and its progenitors in $0 < z < 4$. Our model predicts the observed galaxy main sequence, the mass-metallicity and the fundamental plane of metallicity relations in $0 < z < 4$. It also reproduces the stellar mass evolution of candidate MW progenitors in $0 \lesssim z \lesssim 2.5$, although the star formation rate and gas fraction of the simulated galaxies follow a shallower redshift dependence. We find that while the MW star formation and chemical enrichment are dominated by the contribution of galaxies hosted in Lyman $\alpha$-cooling halos, at z > 6 the contribution of star forming mini-halos is comparable to the star formation rate along the MW merger tree. These systems might then provide an important contribution in the early phases of reionization. A large number of mini-halos with old stellar populations, possibly Population~III stars, are dragged into the MW or survive in the Local Group. At low redshift dynamical effects, such as halo mergers, tidal stripping and halo disruption redistribute the baryonic properties among halo families. These results are critically discussed in light of future improvements including a more sophisticated treatment of radiative feedback and inhomogeneous metal enrichment.