PRISMS GHZ8: Evidence for a Young Burst and Potential Merger Activity at z=10.23
Abstract
UV-bright galaxies in the early Universe provide important constraints on the rapid build-up of stellar mass and the sources responsible for cosmic reionization. However, the physical processes that drive their high UV luminosities remain unclear. Here we report JWST/MIRI LRS spectroscopy of GHZ8, a UV-bright galaxy at z=10.23 with a magnification μ=1.23. The spectrum shows a ∼ 5σ detection for the Hβ-[OIII] complex and ∼ 4σ for Hα line, with fluxes of 3.2±0.9×10−18 and 1.7±0.4×10−18 erg s−1 cm−2, respectively. Based on JWST/NIRCam imaging, we find that GHZ8 consists of two components separated only by 0.16" (≈600 pc): a bright, extended main component and a faint, compact southeastern clump, hereafter referred to as GHZ8-main and GHZ8-SE. Through morphological decomposition, we find demagnified MUV=−19.91±0.10 and −18.03±0.15 mag for GHZ8-main and GHZ8-SE, with blue UV slopes of βUV=−2.53±0.22 and −3.45±0.49, respectively, indicating that both components host young stellar populations. In particular, the extremely blue UV continuum of GHZ8-SE requires an extremely young, ISM-poor stellar population with a high ionizing photon escape fraction, fesc= 0.6−1.0. Combining the UV and Hα luminosities with the results from the spectro-photometric SED fitting, we constrain the star-formation activity of GHZ8-main, and find either a recent, short-lived burst of star formation that is now in its final phases, or continuous star formation over a relatively short period (<50 Myr). GHZ8 therefore provides observational evidence for bursty star formation in a UV-bright galaxy. Globally, GHZ8 may be undergoing a merger-induced starburst, although deeper imaging or spatially resolved kinematic information is required for a more definitive interpretation.
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BibTeX
@misc{lin2026prisms,
title = {{PRISMS GHZ8: Evidence for a Young Burst and Potential Merger Activity at z=10.23}},
author = {Ruqiu Lin and Jorge Zavala and Javier Álvarez-Márquez and Luis Colina and Marco Castellano and Adriano Fontana and Paola Santini and Lorenzo Napolitano and Sarah Kendrew and Alejandro Crespo Gómez and Victoria Salazar and Abdurro'uf and Stefano Carniani and Tiger Hsiao and Yuichi Harikane and Mahmoud Hamed and Takuya Hashimoto and Akio Inoue and Danial Langeroodi and Rui Marques-Chaves and Ikki Mitsuhashi and Yurina Nakazato and Borja Pérez-Díaz and Pierluigi Rinaldi and Carlota Prieto-Jiménez and Ana Varo-O'Ferrall and Fang-Ting Yuan and Shuairu Zhu and Zhen-Ya Zheng},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.40633},
eprint = {2610.40633},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.40633},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - PRISMS GHZ8: Evidence for a Young Burst and Potential Merger Activity at z=10.23
AU - Ruqiu Lin
AU - Jorge Zavala
AU - Javier Álvarez-Márquez
AU - Luis Colina
AU - Marco Castellano
AU - Adriano Fontana
AU - Paola Santini
AU - Lorenzo Napolitano
AU - Sarah Kendrew
AU - Alejandro Crespo Gómez
AU - Victoria Salazar
AU - Abdurro'uf
AU - Stefano Carniani
AU - Tiger Hsiao
AU - Yuichi Harikane
AU - Mahmoud Hamed
AU - Takuya Hashimoto
AU - Akio Inoue
AU - Danial Langeroodi
AU - Rui Marques-Chaves
AU - Ikki Mitsuhashi
AU - Yurina Nakazato
AU - Borja Pérez-Díaz
AU - Pierluigi Rinaldi
AU - Carlota Prieto-Jiménez
AU - Ana Varo-O'Ferrall
AU - Fang-Ting Yuan
AU - Shuairu Zhu
AU - Zhen-Ya Zheng
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.40633
UR - https://arxiv.org/abs/2610.40633
AB - UV-bright galaxies in the early Universe provide important constraints on the rapid build-up of stellar mass and the sources responsible for cosmic reionization. However, the physical processes that drive their high UV luminosities remain unclear. Here we report JWST/MIRI LRS spectroscopy of GHZ8, a UV-bright galaxy at z=10.23 with a magnification μ=1.23. The spectrum shows a ∼ 5σ detection for the Hβ-[OIII] complex and ∼ 4σ for Hα line, with fluxes of 3.2±0.9×10^−18 and 1.7±0.4×10^−18 erg s^−1 cm^−2, respectively. Based on JWST/NIRCam imaging, we find that GHZ8 consists of two components separated only by 0.16" (≈600 pc): a bright, extended main component and a faint, compact southeastern clump, hereafter referred to as GHZ8-main and GHZ8-SE. Through morphological decomposition, we find demagnified M_UV=−19.91±0.10 and −18.03±0.15 mag for GHZ8-main and GHZ8-SE, with blue UV slopes of β_UV=−2.53±0.22 and −3.45±0.49, respectively, indicating that both components host young stellar populations. In particular, the extremely blue UV continuum of GHZ8-SE requires an extremely young, ISM-poor stellar population with a high ionizing photon escape fraction, f_esc= 0.6−1.0. Combining the UV and Hα luminosities with the results from the spectro-photometric SED fitting, we constrain the star-formation activity of GHZ8-main, and find either a recent, short-lived burst of star formation that is now in its final phases, or continuous star formation over a relatively short period (<50 Myr). GHZ8 therefore provides observational evidence for bursty star formation in a UV-bright galaxy. Globally, GHZ8 may be undergoing a merger-induced starburst, although deeper imaging or spatially resolved kinematic information is required for a more definitive interpretation.
ER -