# JADES: The production and escape of ionizing photons from faint Lyman-alpha emitters in the epoch of reionization

**Authors:** Aayush Saxena, Andrew J. Bunker, Gareth C. Jones, Daniel P. Stark, Alex J. Cameron, Joris Witstok, Santiago Arribas, William M. Baker, Stefi Baum, Rachana Bhatawdekar, Rebecca Bowler, Kristan Boyett, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Daniel J. Eisenstein, Ryan Endsley, Kevin Hainline  
**arXiv:** [2306.04536](https://arxiv.org/abs/2306.04536)  
**Date:** 2023-06-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2306.04536v1/

## Key points

- Study presents properties of 16 faint Lyman-alpha emitting galaxies (LAEs) at redshifts > 5.8
- Spectroscopic data from JWST Advanced Deep Extragalactic Survey (JADES) in Hubble Ultra Deep Field/GOODS-S
- LAEs have wide range of redshifts (approx. 5.8 to 8.0) and UV magnitudes (-17 to -20.6)
- Lyman-alpha equivalent widths between approx. 25 and 350 angstroms
- Other rest-optical emission lines detected, allowing for accurate determination of systemic redshifts and velocity offsets
- Faint LAEs consistent with being metal-poor systems with high ionization parameters
- Average ionizing photon production efficiency across LAEs does not strongly evolve with redshift
- Anti-correlation observed between Lyman-alpha escape fraction and velocity offset from systemic
- Strength and velocity offset of Lyman-alpha not correlated with galaxy spectroscopic properties or ionizing photon production efficiency
- Decrease in Lyman-alpha escape fractions with increasing redshift, indicating decrease in sizes of ionized bubbles around LAEs at higher redshifts
- Predictions made for Lyman continuum escape fractions based on various galaxy properties, showing mild increase with redshift
- Correlations derived between ionizing photon output from LAEs and UV magnitude, Lyman-alpha strengths, and redshift for developing reionization models
- Study increases number of faint LAEs detected at redshifts > 6 using deep spectra from JWST observations
- Insights into role of faint LAEs in driving cosmic reionization during this epoch
- Implications discussed for emergent Lyman alpha emission due to increasingly neutral intergalactic medium at high redshifts
- Findings based on Planck Collaboration et al.'s cosmology; magnitudes reported in AB system; distances used proper distances unless specified otherwise.

## Summary

This study presents the properties of 16 faint Lyman-alpha emitting galaxies (LAEs) at redshifts greater than 5.8, using spectroscopic data from the JWST Advanced Deep Extragalactic Survey (JADES) in the Hubble Ultra Deep Field/GOODS-S. These LAEs have a wide range of redshifts, approximately 5.8 to 8.0, and UV magnitudes ranging from -17 to -20.6, with Lyman-alpha equivalent widths between approximately 25 and 350 angstroms. The detection of other rest-optical emission lines in their spectra allows for accurate determination of systemic redshifts and Lyman-alpha velocity offsets, as well as insights into the physical and chemical composition of their stars and interstellar media. The results show that these faint LAEs are consistent with being metal-poor systems with high ionization parameters, similar to the general galaxy population at redshifts greater than 6. The average ionizing photon production efficiency across these LAEs is measured to be log($\xi_{\textrm{ion}}$/erg$^{-1}$ Hz) ≈ 25.56 which does not strongly evolve with redshift. An anti-correlation is observed between Lyman-alpha escape fraction and velocity offset from systemic in line with model expectations. Furthermore, it is found that the strength and velocity offset of Lyman-alpha are not correlated with galaxy spectroscopic properties or ionizing photon production efficiency ($\xi_{\textrm{ion}}$). A decrease in Lyman-alpha escape fractions with increasing redshift is observed indicating a decrease in the sizes of ionized bubbles around LAEs at higher redshifts. Using various galaxy properties predictions for Lyman continuum escape fractions are made for these LAEs which show a mild increase with redshift. Correlations are derived between the ionizing photon output from LAEs and UV magnitude, Lyman-alpha strengths, and redshift which can be used to develop realistic reionization models. This study significantly increases the number of faint LAEs detected at redshifts greater than 6 using deep spectra from JWST observations providing valuable insights into their role in driving cosmic reionization during this epoch as well as discussing implications for emergent Lyman alpha emission due to an increasingly neutral intergalactic medium at high redshifts; companion papers further analyze additional aspects such as clustering size of ionized bubbles around these LAEs etc.. All findings are based on Planck Collaboration et al. 's (2020) cosmology; magnitudes reported in AB system (Oke & Gunn 1983); all distances used proper distances unless otherwise specified.