Dust in the first galaxies

TL;DR

This study uses cosmological simulations and a new model to assess dust extinction in the first galaxies caused by Pop III stars, finding very low average extinction but a measurable maximum in dense regions.

Contribution

It introduces a novel sub-grid model for Pop III star formation and quantifies baseline dust extinction in early galaxies based on halo mass and redshift.

Findings

Maximum extinction from Pop III dust is about 0.07 in E(B-V).

Average extinction is less than 10^-3, indicating minimal overall dust impact.

UV spectral reddening is nearly independent of halo mass and redshift.

Abstract

Using cosmological volume simulations and a custom built sub-grid model for Pop~III star formation, we examine the baseline dust extinction in the first galaxies due to Pop~III metal enrichment in the first billion years of cosmic history. We find that while the most enriched, high-density lines of sight in primordial galaxies can experience a measurable amount of extinction from Pop~III dust ($E(B-V)_{\rm max}=0.07,\ A_{\rm V,max}\approx0.28$), the average extinction is very low with $\left< E(B-V) \right> \lesssim 10^{-3}$. We derive a power-law relationship between dark matter halo mass and extinction of $E(B-V)\propto M_{\rm halo}^{0.80}$. Performing a Monte Carlo parameter study, we establish the baseline reddening of the UV spectra of dwarf galaxies at high redshift due to Pop~III enrichment only. With this method, we find $\left<\beta_{\rm UV}\right>-2.51\pm0.07$, which is both nearly halo mass and redshift independent.