Are High-EW LAEs good analogs for the earliest galaxies? A study on the ionizing conditions and gas properties of LAEs at $2\lesssim z\lesssim7
Abstract
Lyman-α emitters (LAEs) are frequently proposed as analogs of the low-mass, metal-poor galaxies thought to dominate cosmic reionization. In particular, galaxies with large Lyα equivalent widths (EWs) are expected to have not experienced significant chemical enrichment. We test this hypothesis using a sample of 88 LAEs at 2 ≲ z≲ 7, selected from MUSE observations that are undetected in deep HST imaging and subsequently followed up with JWST/NIRSpec spectroscopy. Despite the unprecedented sensitivity of JWST, only 50 of the LAEs exhibit secure counterparts in available deep NIRCam imaging reaching typical 3σ depths of mAB∼30.3 mag, highlighting the intrinsically faint nature of the population. Gas-phase metallicities are inferred by fitting optical emission lines with a grid of BPASS+cloudy photoionization models, while stellar masses are derived from NIRCam photometry through SED fitting. The final sample with secure stellar masses and gas-phase metallicities encompasses only 16 LAEs, occupying regions of standard emission-line diagnostic diagrams consistent with low-metallicity star-forming systems. Although the strong-line metallicity diagnostic R3 appears to decrease with increasing EW, we find no compelling evidence for a strong monotonic relation between EW and gas-phase metallicity when metallicities are inferred through full emission-line fitting. However, galaxies with stronger Lyα emission tend to lie below the average mass-metallicity relation at fixed stellar masses, suggesting that they are preferentially less chemically evolved than typical galaxies of the same mass. We conclude that high-EW LAEs provide useful, though imperfect, analogs of the galaxies thought to drive cosmic reionization, and combining EW with stellar mass may provide a more effective route for identifying the most chemically primitive galaxies.
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BibTeX
@misc{pless2026highew,
title = {{Are High-EW LAEs good analogs for the earliest galaxies? A study on the ionizing conditions and gas properties of LAEs at $2\lesssim z\lesssim7}},
author = {Lena Pless and Themiya Nanayakkara and Karl Glazebrook and Michael Maseda and Jarle Brinchmann and Tanya Urrutia},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21232},
eprint = {2610.21232},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21232},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Are High-EW LAEs good analogs for the earliest galaxies? A study on the ionizing conditions and gas properties of LAEs at $2\lesssim z\lesssim7
AU - Lena Pless
AU - Themiya Nanayakkara
AU - Karl Glazebrook
AU - Michael Maseda
AU - Jarle Brinchmann
AU - Tanya Urrutia
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21232
UR - https://arxiv.org/abs/2610.21232
AB - Lyman-α emitters (LAEs) are frequently proposed as analogs of the low-mass, metal-poor galaxies thought to dominate cosmic reionization. In particular, galaxies with large Lyα equivalent widths (EWs) are expected to have not experienced significant chemical enrichment. We test this hypothesis using a sample of 88 LAEs at 2 ≲ z≲ 7, selected from MUSE observations that are undetected in deep HST imaging and subsequently followed up with JWST/NIRSpec spectroscopy. Despite the unprecedented sensitivity of JWST, only 50 of the LAEs exhibit secure counterparts in available deep NIRCam imaging reaching typical 3σ depths of m_AB∼30.3 mag, highlighting the intrinsically faint nature of the population. Gas-phase metallicities are inferred by fitting optical emission lines with a grid of BPASS+cloudy photoionization models, while stellar masses are derived from NIRCam photometry through SED fitting. The final sample with secure stellar masses and gas-phase metallicities encompasses only 16 LAEs, occupying regions of standard emission-line diagnostic diagrams consistent with low-metallicity star-forming systems. Although the strong-line metallicity diagnostic R3 appears to decrease with increasing EW, we find no compelling evidence for a strong monotonic relation between EW and gas-phase metallicity when metallicities are inferred through full emission-line fitting. However, galaxies with stronger Lyα emission tend to lie below the average mass-metallicity relation at fixed stellar masses, suggesting that they are preferentially less chemically evolved than typical galaxies of the same mass. We conclude that high-EW LAEs provide useful, though imperfect, analogs of the galaxies thought to drive cosmic reionization, and combining EW with stellar mass may provide a more effective route for identifying the most chemically primitive galaxies.
ER -