AEON-z5: A Candidate AGN-driven Outflow Enriching the Circumgalactic Medium at z≃5.23
Abstract
The dispersal of chemically enriched gas from galaxies into their surroundings is a key process in galaxy evolution, yet direct observational evidence at z>5 remains scarce. We present AEON-z5, a galaxy at z~5.23 in the COSMOS field comprising a compact continuum-emitting core surrounded by an extended, line-dominated ionized nebula. JWST/NIRCam imaging shows that Hα+[N II] and Hβ+[O III] emission extends to projected radii of >4 kpc - 2-2.5 times the typical effective radius at the host stellar mass - reaching the outer ISM and the inner CGM. F444W grism data reveal a highly asymmetric Hα+[N II] profile, which we interpret as a bipolar outflow and decompose into three kinematic components. The dominant component has a flux-weighted velocity offset of ~+489 km/s and FWHM~630 km/s, with a wing reaching v84~792 km/s. A tentative detached feature at ΔvLOS~2800 km/s, detected at 1.5σ in the 1D spectrum (2.4σ in the 2D fit), may trace an outflow clump. These kinematics are most coherently explained by an AGN in the core. For the extended nebula, we derive a velocity curve shifting redward with radius, reaching 200-400 km/s at rp~1.3-2.5 kpc - a trend that may reflect an accelerating outflow, corotating gas, or recycled inflow viewed in projection. Crucially, the measured [N II]/Hα ratios imply near-solar N2-based abundances (0.7-1.0 Z⊙), remaining >0.37 Z⊙ after allowing for AGN excitation and calibration systematics. The combination of large extent, enrichment, and extreme kinematics identifies AEON-z5 as a candidate snapshot of feedback-driven metal transport, offering a direct view of how early AGN activity may redistribute chemically processed gas into the CGM within the first ~1.1 billion years.
Related
- The multiphase circumgalactic medium in the epoch of reionization: CII and CIV absorbers around [OIII] emitters
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- From Dispersion to Metallicity: Probing the Milky Way Circumgalactic Medium with Fast Radio Bursts
BibTeX
@misc{wei2026aeonz5,
title = {{AEON-z5: A Candidate AGN-driven Outflow Enriching the Circumgalactic Medium at $z\simeq5.23$}},
author = {Xiaoyang Wei and Zheng Cai and Shiwu Zhang and Fujiang Yu and Yunjing Wu and Shuaiyi Li and Xiaojing Lin and Mingyu Li and Xuelun Mei},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.08264},
eprint = {2609.08264},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.08264},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - AEON-z5: A Candidate AGN-driven Outflow Enriching the Circumgalactic Medium at z≃5.23
AU - Xiaoyang Wei
AU - Zheng Cai
AU - Shiwu Zhang
AU - Fujiang Yu
AU - Yunjing Wu
AU - Shuaiyi Li
AU - Xiaojing Lin
AU - Mingyu Li
AU - Xuelun Mei
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.08264
UR - https://arxiv.org/abs/2609.08264
AB - The dispersal of chemically enriched gas from galaxies into their surroundings is a key process in galaxy evolution, yet direct observational evidence at z>5 remains scarce. We present AEON-z5, a galaxy at z~5.23 in the COSMOS field comprising a compact continuum-emitting core surrounded by an extended, line-dominated ionized nebula. JWST/NIRCam imaging shows that Hα+[N II] and Hβ+[O III] emission extends to projected radii of >4 kpc - 2-2.5 times the typical effective radius at the host stellar mass - reaching the outer ISM and the inner CGM. F444W grism data reveal a highly asymmetric Hα+[N II] profile, which we interpret as a bipolar outflow and decompose into three kinematic components. The dominant component has a flux-weighted velocity offset of ~+489 km/s and FWHM~630 km/s, with a wing reaching v_84~792 km/s. A tentative detached feature at Δv_LOS~2800 km/s, detected at 1.5σ in the 1D spectrum (2.4σ in the 2D fit), may trace an outflow clump. These kinematics are most coherently explained by an AGN in the core. For the extended nebula, we derive a velocity curve shifting redward with radius, reaching 200-400 km/s at r_p~1.3-2.5 kpc - a trend that may reflect an accelerating outflow, corotating gas, or recycled inflow viewed in projection. Crucially, the measured [N II]/Hα ratios imply near-solar N2-based abundances (0.7-1.0 Z_⊙), remaining >0.37 Z_⊙ after allowing for AGN excitation and calibration systematics. The combination of large extent, enrichment, and extreme kinematics identifies AEON-z5 as a candidate snapshot of feedback-driven metal transport, offering a direct view of how early AGN activity may redistribute chemically processed gas into the CGM within the first ~1.1 billion years.
ER -