The Pandora project. II: how non-thermal physics drives bursty star formation and temperate mass-loaded outflows in dwarf galaxies

TL;DR

This study uses high-resolution simulations to show that non-thermal physics like cosmic rays significantly influence bursty star formation and multi-phase outflows in dwarf galaxies, aligning models more closely with observations.

Contribution

It demonstrates that including cosmic rays and radiation in simulations produces more realistic outflows and star formation histories in dwarf galaxies, advancing galaxy formation modeling.

Findings

Cosmic rays produce fast, multi-phase, mass-loaded outflows.

Radiation reduces star formation clustering and feedback strength.

Outflows retain metals within the galaxy, matching observations.

Abstract

Dwarf galaxies provide powerful laboratories for studying galaxy formation physics. Their early assembly, shallow gravitational potentials, and bursty, clustered star formation histories make them especially sensitive to the processes that regulate baryons through multi-phase outflows. Using high-resolution, cosmological zoom-in simulations of a dwarf galaxy from \textit{the Pandora suite}, we explore the impact of stellar radiation, magnetic fields, and cosmic ray feedback on star formation, outflows, and metal retention. We find that our purely hydrodynamical model without non-thermal physics - in which supernova feedback is boosted to reproduce realistic stellar mass assembly - drives violent, overly enriched outflows that suppress the metal content of the host galaxy. Including radiation reduces the clustering of star formation and weakens feedback. However, the additional incorporation of cosmic rays produces fast, mass-loaded, multi-phase outflows consisting of both ionized and neutral gas components, in better agreement with observations. These outflows, which entrain a denser, more temperate ISM, exhibit broad metallicity distributions while preserving metals within the galaxy. Furthermore, the star formation history becomes more bursty, in agreement with recent JWST findings. These results highlight the essential role of non-thermal physics in galaxy evolution and the need to incorporate it in future galaxy formation models.