# Nebular Line Emission During the Epoch of Reionization

## TL;DR

This paper predicts nebular emission line properties of early galaxies during the epoch of reionization using simulations and photoionisation models, aiding future observations with the Webb Telescope.

## Contribution

It combines the Bluetides simulation with photoionisation modeling to forecast nebular emission lines at high redshifts, filling a gap before Webb Telescope data becomes available.

## Key findings

- Good agreement with existing observational constraints on equivalent widths.
- Poorer agreement with luminosity function constraints.
- Predictions will assist in interpreting Webb Telescope observations.

## Abstract

Nebular emission lines associated with galactic HII regions carry information about both physical properties of the ionised gas and the source of ionising photons as well as providing the opportunity of measuring accurate redshifts and thus distances once a cosmological model is assumed. While nebular line emission has been extensively studied at lower redshift there are currently only few constraints within the epoch of reionisation (EoR, $z>6$), chiefly due to the lack of sensitive near-IR spectrographs. However, this will soon change with the arrival of the Webb Telescope providing sensitive near-IR spectroscopy covering the rest-frame UV and optical emission of galaxies in the EoR. In anticipation of Webb we combine the large cosmological hydrodynamical simulation Bluetides with photoionisation modelling to predict the nebular emission line properties of galaxies at $z=8\to 13$. We find good agreement with the, albeit limited, existing direct and indirect observational constraints on equivalent widths though poorer agreement with luminosity function constraints.