A direct black-hole mass measurement in a little red dot at high redshift

Abstract Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad Hα emitters with optically red continua, named little red dots (LRDs) 1 , which comprise 15–30% of the high-redshift broad-line AGN population 2 . Owing to their peculiar properties 3–6 , modelling LRDs with standard AGN scenarios has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black-hole masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to two orders of magnitude 7–10 . Here we report a direct, dynamical black-hole mass measurement in a strongly lensed LRD at a redshift of 7.04. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million solar masses, consistent with virial black-hole mass estimates. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer M BH / M ⁎ > 2 (where M BH is the black-hole mass and M ⁎ is the stellar mass). Such a ‘naked’ black hole, together with its near-pristine environment 11 , indicates that this LRD is a massive black-hole seed caught in its earliest accretion phase.

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Journal
Nature
Published
2026-05-27
DOI
https://doi.org/10.1038/s41586-026-10579-4
Primary Topic
Astrophysical Phenomena and Observations
Type
article
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article

A direct black-hole mass measurement in a little red dot at high redshift

Stephanie Monty, Nicolas Laporte, Jake S. Bennett, Alessandro Trinca et al.
Nature
Astrophysical Phenomena and Observations
article

A direct black-hole mass measurement in a little red dot at high redshift

Stephanie Monty, Nicolas Laporte, Jake S. Bennett, Alessandro Trinca, Saiyang Zhang, Sophie Koudmani, A. Marconi, C. Marconcini, Rosa Valiante, Volker Bromm, Marta Volonteri, Eleonora Parlanti, Santiago Arribas, I Juodžbalis, A J Bunker, S Carniani, Sandro Tacchella, B Robertson, S Charlot, P G Pérez-González, G C Jones, H Übler, F D’Eugenio, M Perna, Boyuan Liu, Debora Sijacki, Jan Scholtz, Joris Witstok, Pratika Dayal, Xihan Ji, Kohei Inayoshi, Jianwei Lyu, Giovanni Mazzolari, Andrew Fabian, Lucy R. Ivey, Eiichi Egami, Yuki Isobe, Roberto Maiolino, Raffaella Schneider, Giovanni Cresci
article en

Abstract

Abstract Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad Hα emitters with optically red continua, named little red dots (LRDs) 1 , which comprise 15–30% of the high-redshift broad-line AGN population 2 . Owing to their peculiar properties 3–6 , modelling LRDs with standard AGN scenarios has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black-hole masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to two orders of magnitude 7–10 . Here we report a direct, dynamical black-hole mass measurement in a strongly lensed LRD at a redshift of 7.04. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million solar masses, consistent with virial black-hole mass estimates. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer M BH / M ⁎ > 2 (where M BH is the black-hole mass and M ⁎ is the stellar mass). Such a ‘naked’ black hole, together with its near-pristine environment 11 , indicates that this LRD is a massive black-hole seed caught in its earliest accretion phase.

NatureVol. 653(8116)
University of Insubria (IT), University of Copenhagen (DK), Centre National de la Recherche Scientifique (FR), University of Arizona (US), University of Hertfordshire (GB), Waseda University (JP), Scuola Normale Superiore (IT), University of Groningen (NL), University of California, Santa Cruz (US), University of Toronto (CA), Peking University (CN), Aix-Marseille Université (FR), Heidelberg University (DE), University of Cambridge (GB), Arcetri Astrophysical Observatory (IT), Astronomical Observatory of Rome (IT), Institut d'Astrophysique de Paris (FR), Sorbonne Université (FR), University of Oxford (GB), Max Planck Institute for Extraterrestrial Physics (DE), Laboratoire d’Astrophysique de Marseille (FR), Kavli Institute for Theoretical Sciences (CN), Canadian Institute for Theoretical Astrophysics (CA), Institute of Astronomy (RU), Center for Astrophysics Harvard & Smithsonian (US), Centro de Astrobiología (ES), University of Florence (IT), University College London (GB), Sapienza University of Rome (IT), The University of Texas at Austin (US), National Institute for Astrophysics (IT)
National Aeronautics and Space Administration, Space Telescope Science Institute, UK Research and Innovation, European Space Agency, European Commission, National Research Foundation, Danmarks Grundforskningsfond, National Natural Science Foundation of China, Ministerio de Ciencia e Innovación, Huo Family Foundation, Canadian Space Agency, Science and Technology Facilities Council, Agencia Estatal de Investigación, European Social Fund
Openalex Percentile: Top 6%
Astrophysical Phenomena and Observations
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