# The edge of galaxy formation III: The effects of warm dark matter on Milky Way satellites and field dwarfs

## TL;DR

This study uses hydrodynamical simulations to compare how warm dark matter and cold dark matter influence the formation, evolution, and observable properties of dwarf galaxies and satellites in the Milky Way, revealing delayed star formation and structural differences.

## Contribution

It provides the first detailed hydrodynamical simulation comparison of WDM and CDM effects on dwarf galaxies and satellites, highlighting differences in star formation and structural evolution.

## Key findings

- WDM delays star formation in dwarf galaxies.
- WDM halos have younger stellar populations by about two Gyrs.
- WDM satellites are more susceptible to tidal stripping but can survive longer in steeper halos.

## Abstract

In this third paper of the series, we investigate the effects of warm dark matter with a particle mass of $m_\mathrm{WDM}=3\,\mathrm{keV}$ on the smallest galaxies in our Universe. We present a sample of 21 hydrodynamical cosmological simulations of dwarf galaxies and 20 simulations of satellite-host galaxy interaction that we performed both in a Cold Dark Matter (CDM) and Warm Dark Matter (WDM) scenario. In the WDM simulations, we observe a higher critical mass for the onset of star formation. Structure growth is delayed in WDM, as a result WDM haloes have a stellar population on average two Gyrs younger than their CDM counterparts. Nevertheless, despite this delayed star formation, CDM and WDM galaxies are both able to reproduce the observed scaling relations for velocity dispersion, stellar mass, size, and metallicity at $z=0$. WDM satellite haloes in a Milky Way mass host are more susceptible to tidal stripping due to their lower concentrations, but their galaxies can even survive longer than the CDM counterparts if they live in a dark matter halo with a steeper central slope. In agreement with our previous CDM satellite study we observe a steepening of the WDM satellites' central dark matter density slope due to stripping. The difference in the average stellar age for satellite galaxies, between CDM and WDM, could be used in the future for disentangling these two models.