# Evolution of the Lyman-α emitting fraction and UV properties of lensed star-forming galaxies between 2.9 < z < 6.7

**Authors:** Ilias Goovaerts, Roser Pello, Tran Thi Thai, Pham Tuan-Anh, Johan Richard, Adélaïde Claeyssens, Emile Carinos, Geoffroy de la Vieuville, Jorryt Matthee  
**arXiv:** [2307.15559](https://arxiv.org/abs/2307.15559)  
**Date:** 2023-07-28  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.15559v1/

## Key points

- Study focuses on the role of faint galaxies in the reionization of the Universe
- Utilizes four galaxy clusters from LLAMAS to select a population of intrinsically faint LBGs and LAEs
- Redshift evolution of Lyman-alpha emitter fraction consistent with previous results, indicating increasingly neutral IGM above z = 6
- Fraction of Lyman-alpha emitters higher for UV-brighter half of the sample compared to UV-fainter half, more pronounced at higher redshifts
- Presence of a population consisting of low Lyman-alpha EW, UV-bright galaxies situated in reionized bubbles
- Stronger LAEs generally have fainter UV magnitudes and steeper UV slopes
- Provides insights into evolution of Lyman alpha emitter fraction and UV properties between redshifts 2.9 and 6.7
- Unexpected finding suggests unique population in reionized bubbles contributes to understanding role of faint galaxies in reionization process

## Summary

This study focuses on the role of faint galaxies in the reionization of the Universe and aims to provide insights into this epoch by examining their properties and the fraction of Lyman-alpha emitters (LAEs) among them. The researchers utilize four galaxy clusters from the Lensed Lyman-alpha MUSE Arcs Sample (LLAMAS), which also have deep HST photometry, to select a population of intrinsically faint Lyman Break Galaxies (LBGs) and LAEs. By studying the interrelation between these two populations, their properties, and the fraction of LBGs displaying Lyman-alpha emission, the researchers gain valuable information about the evolution of LAEs and UV properties in lensed star-forming galaxies. The use of lensing clusters allows access to an intrinsically faint population, resulting in the largest sample collected for this purpose: 263 LAEs and 972 LBGs between redshifts of 2.9 and 6.7. The findings reveal a redshift evolution of the Lyman-alpha emitter fraction consistent with previous results, showing diminished values above z = 6, indicating an increasingly neutral intervening intergalactic medium (IGM). Further analysis considering different limits on Lyman-alpha equivalent width (EW) and absolute UV magnitudes (M1500) reveals that the fraction of Lyman-alpha emitters is higher for the UV-brighter half of the sample compared to the UV-fainter half. This difference becomes more pronounced at higher redshifts. This unexpected result suggests the presence of a population consisting of low Lyman-alpha EW, UV-bright galaxies situated in reionized bubbles. This finding is particularly intriguing when considering similar UV-bright objects with low Lyman-alpha EW recently detected around the epoch of reionization. Moreover, this study extends previously observed trends among LBGs as galaxies with high star formation rates and low dust content as well as observing that stronger LAEs generally have fainter UV magnitudes and steeper UV slopes. In conclusion, this study provides valuable insights into the evolution of the Lyman alpha emitter fraction and UV properties of lensed star forming galaxies between redshifts 2.9 and 6.7. The unexpected finding that there is a higher Lyman alpha emitter fraction among brighter galaxies suggests that there is a unique population situated in reionized bubbles which contributes to our understanding about how faint galaxies play a role in reionization process as well as providing important context for similar objects detected during epochs near reionization.