C3PO: A Lyα Emitting Galaxy at z ∼ 9
Abstract
We present deep, >10 hr, JWST NIRSpec G140M and G395M observations of a previously known galaxy C3PO-8447 at z=8.99781. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Lyα emission with an escape fraction of 1.5±0.3% and a velocity offset of 210±80 km s−1, making C3PO-8447 the third Lyα emitting galaxy confirmed at z≳ 9. The galaxy has a low stellar mass of 2.2±0.1× 107 M⊙, a young stellar age of 1.6±0.2 Myr, and a low oxygen abundance of 12+log(O/H) = 7.50±0.08. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Lyα escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius R ∼ 0.07 to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale galaxy overdensity around C3PO-8447 or a significant contribution from nearby galaxies to its ionizing photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously star-forming galaxy during the early stages of cosmic reionization.
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BibTeX
@misc{hu2026c3po,
title = {{C3PO: A Lyα Emitting Galaxy at $z \sim 9$}},
author = {Weida Hu and Casey Papovich and Taylor A. Hutchison and Rebecca L. Larson and Pablo Arrabal Haro and Steven L. Finkelstein and Nikko J. Cleri and Lu Shen and Jiayang Yang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03608},
eprint = {2609.03608},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03608},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - C3PO: A Lyα Emitting Galaxy at z ∼ 9
AU - Weida Hu
AU - Casey Papovich
AU - Taylor A. Hutchison
AU - Rebecca L. Larson
AU - Pablo Arrabal Haro
AU - Steven L. Finkelstein
AU - Nikko J. Cleri
AU - Lu Shen
AU - Jiayang Yang
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03608
UR - https://arxiv.org/abs/2609.03608
AB - We present deep, >10 hr, JWST NIRSpec G140M and G395M observations of a previously known galaxy C3PO-8447 at z=8.99781. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Lyα emission with an escape fraction of 1.5±0.3% and a velocity offset of 210±80 km s^−1, making C3PO-8447 the third Lyα emitting galaxy confirmed at z≳ 9. The galaxy has a low stellar mass of 2.2±0.1× 10^7 M_⊙, a young stellar age of 1.6±0.2 Myr, and a low oxygen abundance of 12+log(O/H) = 7.50±0.08. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Lyα escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius R ∼ 0.07 to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale galaxy overdensity around C3PO-8447 or a significant contribution from nearby galaxies to its ionizing photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously star-forming galaxy during the early stages of cosmic reionization.
ER -