First Light And Reionisation Epoch Simulations (FLARES) XI: [OIII] emitting galaxies at $5<z<10$

TL;DR

This paper uses FLARES simulations to predict [OIII] emission properties of high-redshift galaxies, comparing results with JWST observations and discussing discrepancies and potential explanations.

Contribution

It provides new predictions for [OIII] luminosity functions, equivalent widths, and their correlations with galaxy properties at z>5, aiding interpretation of JWST data.

Findings

Predicted [OIII] luminosity function aligns with observations.

Average equivalent widths match observational data.

Discrepancies include underprediction of high-EW sources.

Abstract

JWST has now made it possible to probe the rest-frame optical line emission of high-redshift galaxies extending to z~9, and potentially beyond. To aid in the interpretation of these emerging constraints, in this work we explore predictions for [OIII] emission in high-redshift galaxies using the First Light and Reionisation Epoch Simulations (FLARES). We produce predictions for the [OIII] luminosity function, its correlation with the UV luminosity, and the distribution of equivalent widths (EWs). We also explore how the [OIII] EW correlates with physical properties including specific star formation rate, metallicity, and dust attenuation. Our predictions are largely consistent with recent observational constraints on the luminosity function, average equivalent widths, and line ratios. However, they fail to reproduce the observed tail of high-EW sources and the number density of extreme line emitters. Possibilities to explain these discrepancies include an additional source of ionising photons and/or greater stochasticity in star formation in the model or photometric scatter and/or bias in the observations. With JWST now rapidly building larger samples and a wider range of emission lines the answer to this remaining discrepancy should be available imminently.