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Main Authors: Harikane, Yuichi, Perez-Gonzalez, Pablo G., Alvarez-Marquez, Javier, Ouchi, Masami, Nakazato, Yurina, Ono, Yoshiaki, Nakajima, Kimihiko, Umeda, Hiroya, Isobe, Yuki, Xu, Yi, Zhang, Yechi
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2601.21833
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author Harikane, Yuichi
Perez-Gonzalez, Pablo G.
Alvarez-Marquez, Javier
Ouchi, Masami
Nakazato, Yurina
Ono, Yoshiaki
Nakajima, Kimihiko
Umeda, Hiroya
Isobe, Yuki
Xu, Yi
Zhang, Yechi
author_facet Harikane, Yuichi
Perez-Gonzalez, Pablo G.
Alvarez-Marquez, Javier
Ouchi, Masami
Nakazato, Yurina
Ono, Yoshiaki
Nakajima, Kimihiko
Umeda, Hiroya
Isobe, Yuki
Xu, Yi
Zhang, Yechi
contents One of the major discoveries by the James Webb Space Telescope (JWST) is the identification of a large population of luminous galaxies at $z>10$, challenging theoretical models for early galaxy formation. The unexpectedly high number density of these systems has triggered intense debate about potential differences in the physical properties of galaxies at such extreme redshifts and those at lower redshift. However, progress has been limited by the lack of rest-frame optical diagnostics, which are critical for constraining the key properties. Here we present deep JWST/MIRI observations of a UV-luminous galaxy at $z=11.04$, CEERS2-588, only 400 Myr after the Big Bang. CEERS2-588 is detected in the MIRI F560W and F770W bands, while deep MIRI/MRS spectroscopy yields no detection of H$α$ or [OIII]$\lambda5007$ line, revealing a prominent Balmer break detected for the first time at $z>10$. Spectral energy distribution (SED) fitting indicates an extended star formation history possibly reaching $z>15$, followed by rapid quenching within the recent $\sim10$ Myr, in stark contrast to other $z>10$ galaxies. The MIRI detections also significantly improve our stellar mass estimate to $\mathrm{log}(M_*/M_\odot)=9.1^{+0.1}_{-0.1}$, making CEERS2-588 the most massive galaxy securely confirmed at $z>10$. Remarkably, the inferred gas-phase metallicity is near solar, exceeding predictions from current theoretical models. These results suggest that efficient starbursts play a key role in producing the abundant luminous galaxy population in the early universe.
format Preprint
id arxiv_https___arxiv_org_abs_2601_21833
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A UV-Luminous Galaxy at z=11 with Surprisingly Weak Star Formation Activity
Harikane, Yuichi
Perez-Gonzalez, Pablo G.
Alvarez-Marquez, Javier
Ouchi, Masami
Nakazato, Yurina
Ono, Yoshiaki
Nakajima, Kimihiko
Umeda, Hiroya
Isobe, Yuki
Xu, Yi
Zhang, Yechi
Astrophysics of Galaxies
One of the major discoveries by the James Webb Space Telescope (JWST) is the identification of a large population of luminous galaxies at $z>10$, challenging theoretical models for early galaxy formation. The unexpectedly high number density of these systems has triggered intense debate about potential differences in the physical properties of galaxies at such extreme redshifts and those at lower redshift. However, progress has been limited by the lack of rest-frame optical diagnostics, which are critical for constraining the key properties. Here we present deep JWST/MIRI observations of a UV-luminous galaxy at $z=11.04$, CEERS2-588, only 400 Myr after the Big Bang. CEERS2-588 is detected in the MIRI F560W and F770W bands, while deep MIRI/MRS spectroscopy yields no detection of H$α$ or [OIII]$\lambda5007$ line, revealing a prominent Balmer break detected for the first time at $z>10$. Spectral energy distribution (SED) fitting indicates an extended star formation history possibly reaching $z>15$, followed by rapid quenching within the recent $\sim10$ Myr, in stark contrast to other $z>10$ galaxies. The MIRI detections also significantly improve our stellar mass estimate to $\mathrm{log}(M_*/M_\odot)=9.1^{+0.1}_{-0.1}$, making CEERS2-588 the most massive galaxy securely confirmed at $z>10$. Remarkably, the inferred gas-phase metallicity is near solar, exceeding predictions from current theoretical models. These results suggest that efficient starbursts play a key role in producing the abundant luminous galaxy population in the early universe.
title A UV-Luminous Galaxy at z=11 with Surprisingly Weak Star Formation Activity
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2601.21833