LYRA II: Cosmological dwarf galaxy formation with inhomogeneous Population III enrichment

TL;DR

This paper presents high-resolution cosmological simulations of dwarf galaxy formation, exploring inhomogeneous Population III star enrichment and comparing different subgrid models to observed Local Group dwarf galaxy properties.

Contribution

Introduces LYRA, a novel high-resolution galaxy formation model with inhomogeneous Population III enrichment, and analyzes its impact on dwarf galaxy evolution and properties.

Findings

The simulated galaxy matches observed stellar mass, size, and metallicity relations.

Star formation history is characterized by short, bursty episodes with re-ignitions due to mergers.

Dark matter profile remains cuspy, with no core formation observed.

Abstract

We present the simulation of a $2\times10^9 M_\odot$ halo mass cosmological dwarf galaxy run to $z=0$ at 4 solar mass gas resolution with resolved supernova feedback. We compare three simple subgrid implementations for the inhomogeneous chemical enrichment from Population III stars and compare them to constraints from Local Group dwarf galaxies. The employed model, LYRA, is a novel high resolution galaxy formation model built for the moving mesh code AREPO, which is marked by a resolved multi-phase interstellar medium, single stars and individual supernova events. The resulting reionization relic is characterized by a short ($<1.5$ Gyr) star formation history that is repeatedly brought to a standstill by violent bursts of feedback. Star formation is reignited for a short duration due to a merger at $z\approx4$ and then again at $z\approx0.2-0$ after sustained gas accretion. Our model $z=0$ galaxy matches the stellar mass, size, stellar kinematics and metallicity relations of Local Group dwarf galaxies well. The dark matter profile does not exhibit a core in any version of the model. We show that the host halo masses of Population III stars affect the assembly history of dwarf galaxies. This manifests itself through the initial gaseous collapse in the progenitor halos, affecting the central density of the stellar component and through the accretion of luminous substructure.