Cosmological Simulations of Dwarf Galaxies with Cosmic Ray Feedback

TL;DR

This study uses cosmological simulations to explore how cosmic ray feedback influences dwarf galaxy formation, revealing that cosmic rays promote disk-like structures and match observed rotation relations, but do not create dark matter cores.

Contribution

It demonstrates the effects of cosmic ray feedback with diffusion on dwarf galaxy morphology, star formation, and dark matter profiles, providing new insights into galaxy evolution modeling.

Findings

Cosmic ray feedback leads to disk-dominated galaxies with flat rotation curves.

CR simulations match the baryonic Tully-Fisher relation.

CR feedback galaxies retain cuspy dark matter profiles, unlike thermal feedback ones.

Abstract

We perform zoom-in cosmological simulations of a suite of dwarf galaxies, examining the impact of cosmic-rays generated by supernovae, including the effect of diffusion. We first look at the effect of varying the uncertain cosmic ray parameters by repeatedly simulating a single galaxy. Then we fix the comic ray model and simulate five dwarf systems with virial masses range from 8-30 $\times 10^{10}$ Msun. We find that including cosmic ray feedback (with diffusion) consistently leads to disk dominated systems with relatively flat rotation curves and constant star formation rates. In contrast, our purely thermal feedback case results in a hot stellar system and bursty star formation. The CR simulations very well match the observed baryonic Tully-Fisher relation, but have a lower gas fraction than in real systems. We also find that the dark matter cores of the CR feedback galaxies are cuspy, while the purely thermal feedback case results in a substantial core.