Modeling small galaxies during the Epoch of Reionisation

TL;DR

This paper investigates how the bursty star formation in small galaxies during the Epoch of Reionisation causes variability in their ionising efficiency, affecting their detectability by JWST.

Contribution

It introduces high-resolution simulations linking star formation burstiness to escape fraction variability in small galaxies during reionisation.

Findings

Escape fraction variability correlates with star formation rate fluctuations.

Small galaxies exhibit high scatter in ionising efficiency.

Implications for JWST observations of early galaxies.

Abstract

Small galaxies are thought to be the main contributors to the ionising budget of the Universe before reionisation was complete. There have been a number of numerical studies trying to quantify their ionising efficiency through the escape fraction $f_{esc}$. While there is a clear trend that $f_{esc}$ is higher for smaller haloes, there is a large scatter in the distribution of $f_{esc}$ for a single halo mass. We propose that this is due to the intrinsic burstiness of star formation in low mass galaxies. We performed high resolution radiative hydrodynamics simulations with Ramses-RT to model the evolution of three galaxies and their ionising efficiency. We found that the variability of $f_{esc}$ follows that of the star formation rate. We then discuss the consequences of this variability on the observability of such galaxies by JWST.