Revisiting the Claim for a Direct-collapse Black Hole in UHZ1 at z = 10.05
9 affiliations
- 1University of Michigan
- 2X-ray Astrophysics Laboratory
- 3University College London
- 4University of California
- 5Universitá degli Studi di Milano-Bicocca
- 6Center for Astrophysics
- 7Harvard University
- 8University of Utah
- 9Peking University
Abstract
We reassess the direct collapse black hole (DCBH) interpretation of UHZ1 (UNCOVER-26185), a gravitationally lensed galaxy at z spec = 10.054. That interpretation rests on a hard (2–7 keV) X-ray excess detected with Chandra, attributed to a Compton-thick AGN with an inferred 2–10 keV luminosity of L X,int ∼ 10 ⁴⁶ erg s ⁻¹ (Á. Bogdán et al. 2024). The resulting extreme X-ray to rest-frame optical–IR ratio was taken as the hallmark signature of an “outsize black hole galaxy” at cosmic dawn. We analyze the full 2.2 Ms Chandra imaging dataset—including 0.95 Ms of unpublished observations—and present new JWST/MIRI photometry at λ obs > 5 μ m. Across the full range of plausible Chandra data reductions, the 2–7 keV excess at the position of UHZ1 reaches a significance of only 2.0–2.9 σ ; the originally reported 4.2–4.4 σ detection is sensitive to the specific astrometric alignment adopted and is not robustly reproducible. Moreover, the hard X-ray signal does not grow with the additional exposure, contrary to expectations for a steady source, indicating that any excess is not persistent. UHZ1 is also undetected in all nine MIRI imaging bands. Fitting red/obscured AGN SED templates to the tightest MIRI upper limit, we constrain the bolometric luminosity of any buried AGN to L bol < 1.3 × 10 ⁴⁵ erg s ⁻¹ . These conclusions are further supported by independent JWST spectroscopy, which reveals no AGN signatures in the rest-frame UV or optical. Taken together, the multiwavelength data paint a consistent picture of UHZ1 as a low-mass, metal-poor, star-forming galaxy in the early Universe, with no compelling evidence for a luminous obscured AGN, regardless of its proposed formation channel.
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BibTeX
@article{zou2026revisiting,
title = {{Revisiting the Claim for a Direct-collapse Black Hole in UHZ1 at z = 10.05}},
author = {Fan Zou and Elena Gallo and Zihao Zuo and Edmund Hodges-Kluck and Dieu D. Nguyen and Guido Roberts-Borsani and Piero Madau and Fabio Pacucci and Anil C. Seth and Tommaso Treu and Shouyi Wang},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea0cc},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea0cc},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Revisiting the Claim for a Direct-collapse Black Hole in UHZ1 at z = 10.05
AU - Fan Zou
AU - Elena Gallo
AU - Zihao Zuo
AU - Edmund Hodges-Kluck
AU - Dieu D. Nguyen
AU - Guido Roberts-Borsani
AU - Piero Madau
AU - Fabio Pacucci
AU - Anil C. Seth
AU - Tommaso Treu
AU - Shouyi Wang
PY - 2026
DA - 2026/10/14
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea0cc
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea0cc
AB - We reassess the direct collapse black hole (DCBH) interpretation of UHZ1 (UNCOVER-26185), a gravitationally lensed galaxy at z spec = 10.054. That interpretation rests on a hard (2–7 keV) X-ray excess detected with Chandra, attributed to a Compton-thick AGN with an inferred 2–10 keV luminosity of L X,int ∼ 10 ⁴⁶ erg s ⁻¹ (Á. Bogdán et al. 2024). The resulting extreme X-ray to rest-frame optical–IR ratio was taken as the hallmark signature of an “outsize black hole galaxy” at cosmic dawn. We analyze the full 2.2 Ms Chandra imaging dataset—including 0.95 Ms of unpublished observations—and present new JWST/MIRI photometry at λ obs > 5 μ m. Across the full range of plausible Chandra data reductions, the 2–7 keV excess at the position of UHZ1 reaches a significance of only 2.0–2.9 σ ; the originally reported 4.2–4.4 σ detection is sensitive to the specific astrometric alignment adopted and is not robustly reproducible. Moreover, the hard X-ray signal does not grow with the additional exposure, contrary to expectations for a steady source, indicating that any excess is not persistent. UHZ1 is also undetected in all nine MIRI imaging bands. Fitting red/obscured AGN SED templates to the tightest MIRI upper limit, we constrain the bolometric luminosity of any buried AGN to L bol < 1.3 × 10 ⁴⁵ erg s ⁻¹ . These conclusions are further supported by independent JWST spectroscopy, which reveals no AGN signatures in the rest-frame UV or optical. Taken together, the multiwavelength data paint a consistent picture of UHZ1 as a low-mass, metal-poor, star-forming galaxy in the early Universe, with no compelling evidence for a luminous obscured AGN, regardless of its proposed formation channel.
SN - 0004-637X
SN - 1538-4357
ER -