The DREAMS Project: Disentangling the Impact of Halo-to-Halo Variance and Baryonic Feedback on Milky Way Satellite Galaxies

TL;DR

This study uses large-scale simulations to assess how baryonic physics and halo-to-halo variance influence the properties of Milky Way satellite galaxies, finding that variance dominates over baryonic modeling uncertainties.

Contribution

It demonstrates that halo-to-halo variance has a greater impact than baryonic physics uncertainties on satellite galaxy predictions in cosmological simulations.

Findings

Halo-to-halo variance exceeds baryonic physics uncertainties in satellite properties.

Supernova wind energy significantly affects satellite stellar mass and size.

Baryonic modeling uncertainties are generally subdominant to halo variance.

Abstract

We analyze the properties of satellite galaxies around 1,024 Milky Way-mass hosts from the DREAMS Project, simulated within a $\Lambda$CDM cosmology. Utilizing the TNG galaxy-formation model, the DREAMS simulations incorporate both baryonic physics and cosmological uncertainties for a large sample of galaxies with diverse environments and formation histories. We investigate the relative impact of the physical uncertainty from the galaxy-formation model on predicted satellite properties using four metrics: the satellite stellar mass function, radial distribution, inner slope of dark matter density profile, and stellar half-light radius. We compare these predictions to observations from the SAGA Survey and the DREAMS N-body simulations and find that uncertainties from baryonic physics modeling are subdominant to the scatter arising from halo-to-halo variance. Where baryonic modeling does affect satellites, the supernova wind energy has the largest effect on the satellite properties that we investigate. Specifically, increased supernova wind energy suppresses the stellar mass of satellites and results in more extended stellar half-light radii. The adopted wind speed has only a minor impact, and other astrophysical and cosmological parameters show no measurable effect. Our findings highlight the robustness of satellite properties against uncertainties in baryonic physics modeling.