LATED: Lyα-anchored photometric selection of candidate metal-free and extremely metal-poor star formation from the end of reionisation to cosmic noon
Abstract
Cosmological simulations allow a low-level tail of Population III (Pop III) star formation to persist to z=2−6. Spectroscopic confirmation is expensive, so an efficient photometric pre-selection is needed. We present LATED (Lyman-Alpha Tomography of Extremely Metal-poor Domains), which selects metal-free and extremely metal-poor candidates from a Lyα-emitter parent sample using strong-line diagnostics. The method requires three bands and two colours, x=mOIII−mHα and y=mHα−mcont, which trace oxygen abundance and the Hα equivalent width, respectively. Requiring that the filters simultaneously contain [O III]+Hβ and Hα, together with a Lyα parent selection, defines five windows spanning z=1.92−6.60 (four JWST/NIRCam, one Roman/WFI). The criteria, x≥ xmin(z) and y≤ ymax(z), are set by the per-redshift extrema of a forward-modelled Pop III template locus. Ordinary metal-enriched star-forming and AGN templates fall outside the selection region, and possible contaminants such as little red dots are flagged by their multi-band colours. To check contamination empirically, we apply LATED to 1126 JADES spectroscopic galaxies, and no source is selected in the four NIRCam windows. We release a Python package which converts the same photometry into R3=[O III]/Hβ as a measurement or upper limit, reproducing JADES spectroscopy with small 0.12 dex scatter. Applied to 85 archival MUSE Lyα emitters in Abell 2744, LATED recovers the confirmed extremely metal-poor galaxy AMORE6 and reveals three new candidates at z=3−5. Photometry alone cannot establish a metal-free nature. LATED delivers prioritised candidates for spectroscopic follow-up, providing a scalable route toward a systematic census of late-time Pop III star formation.
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BibTeX
@misc{li2026lated,
title = {{LATED: Ly$α$-anchored photometric selection of candidate metal-free and extremely metal-poor star formation from the end of reionisation to cosmic noon}},
author = {Mingyu Li and Zheng Cai and Roberto Maiolino and Fuyan Bian and Sijia Cai and Francesco D'Eugenio and Qiao Duan and Eiichi Egami and Xiaohui Fan and Yuki Isobe and Xihan Ji and Gareth C. Jones and Maria Koller and Xiaojing Lin and Boyuan Liu and Christopher C. Lovell and Kimihiko Nakajima and Masami Ouchi and Robert G. Pascalau and Zijin Su and Jan Scholtz and Fengwu Sun and Sandro Tacchella and Hannah Übler and Yunjing Wu and Fujiang Yu and Zijian Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.24588},
eprint = {2609.24588},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24588},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - LATED: Lyα-anchored photometric selection of candidate metal-free and extremely metal-poor star formation from the end of reionisation to cosmic noon
AU - Mingyu Li
AU - Zheng Cai
AU - Roberto Maiolino
AU - Fuyan Bian
AU - Sijia Cai
AU - Francesco D'Eugenio
AU - Qiao Duan
AU - Eiichi Egami
AU - Xiaohui Fan
AU - Yuki Isobe
AU - Xihan Ji
AU - Gareth C. Jones
AU - Maria Koller
AU - Xiaojing Lin
AU - Boyuan Liu
AU - Christopher C. Lovell
AU - Kimihiko Nakajima
AU - Masami Ouchi
AU - Robert G. Pascalau
AU - Zijin Su
AU - Jan Scholtz
AU - Fengwu Sun
AU - Sandro Tacchella
AU - Hannah Übler
AU - Yunjing Wu
AU - Fujiang Yu
AU - Zijian Zhang
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.24588
UR - https://arxiv.org/abs/2609.24588
AB - Cosmological simulations allow a low-level tail of Population III (Pop III) star formation to persist to z=2−6. Spectroscopic confirmation is expensive, so an efficient photometric pre-selection is needed. We present LATED (Lyman-Alpha Tomography of Extremely Metal-poor Domains), which selects metal-free and extremely metal-poor candidates from a Lyα-emitter parent sample using strong-line diagnostics. The method requires three bands and two colours, x=m_OIII−m_Hα and y=m_Hα−m_cont, which trace oxygen abundance and the Hα equivalent width, respectively. Requiring that the filters simultaneously contain [O III]+Hβ and Hα, together with a Lyα parent selection, defines five windows spanning z=1.92−6.60 (four JWST/NIRCam, one Roman/WFI). The criteria, x≥ x_min(z) and y≤ y_max(z), are set by the per-redshift extrema of a forward-modelled Pop III template locus. Ordinary metal-enriched star-forming and AGN templates fall outside the selection region, and possible contaminants such as little red dots are flagged by their multi-band colours. To check contamination empirically, we apply LATED to 1126 JADES spectroscopic galaxies, and no source is selected in the four NIRCam windows. We release a Python package which converts the same photometry into R3=[O III]/Hβ as a measurement or upper limit, reproducing JADES spectroscopy with small 0.12 dex scatter. Applied to 85 archival MUSE Lyα emitters in Abell 2744, LATED recovers the confirmed extremely metal-poor galaxy AMORE6 and reveals three new candidates at z=3−5. Photometry alone cannot establish a metal-free nature. LATED delivers prioritised candidates for spectroscopic follow-up, providing a scalable route toward a systematic census of late-time Pop III star formation.
ER -