CAPERS-LRD-z9: A Gas-enshrouded Little Red Dot Hosting a Broad-line Active Galactic Nucleus at z = 9.288

Authors

• Anthony J. Taylor, The University of Texas at Austin
• Vasily Kokorev, The University of Texas at Austin
• Dale D. Kocevski, Colby College
• Hollis B. Akins, The University of Texas at Austin
• Fergus Cullen, University of Edinburgh, Institute for Astronomy
• Mark Dickinson, NOIRLab
• Steven L. Finkelstein, The University of Texas at Austin
• Pablo Arrabal Haro, NASA Goddard Space Flight Center
• Volker Bromm, The University of Texas at Austin
• Mauro Giavalisco, University of Massachusetts Amherst
• Kohei Inayoshi, Peking University
• Stéphanie Juneau, NOIRLab
• Gene C.K. Leung, MIT Kavli Institute for Astrophysics and Space Research
• Pablo G. Pérez-González, CSIC-INTA - Centro de Astrobiología (CAB)
• Rachel S. Somerville, Simons Foundation
• Jonathan R. Trump, University of Connecticut
• Ricardo O. Amorín, CSIC - Instituto de Astrofísica de Andalucía (IAA)
• Guillermo Barro, University of the PacificFollow
• Denis Burgarella, Laboratoire d'Astrophysique de Marseille
• Madisyn Brooks, University of Connecticut
• Adam C. Carnall, University of Edinburgh, Institute for Astronomy

Document Type

Article

Publication Title

Astrophysical Journal Letters

Department

Physics

ISSN

20418213

Volume

989

Issue

1

DOI

10.3847/2041-8213/ade789

First Page

1

Last Page

18

Publication Date

8-6-2025

Abstract

We present CAPERS-LRD-z9, a little red dot (LRD) that we confirm to be a z = 9.288 broad-line active galactic nucleus (BLAGN). First identified as a high-redshift LRD candidate from PRIMER NIRCam photometry, follow-up NIRSpec/PRISM spectroscopy of CAPERS-LRD-z9 from the CANDELS-Area Prism Epoch of Reionization Survey (CAPERS) has revealed a broad 3500 km s⁻¹ full width at half-maximum Hβ emission line and narrow [O iii] λλ4959, 5007 lines, indicative of a BLAGN. Based on the broad Hβ line, we compute a canonical black hole mass of log ( M BH / M ⊙ ) = 7.58 ± 0.15 , although full consideration of systematic uncertainties yields a conservative range of 6.65 < log ( M BH / M ⊙ ) < 8.50 . These observations suggest that either a massive black hole seed or a lighter stellar remnant seed undergoing periods of super-Eddington accretion is necessary to grow such a massive black hole in ≲500 Myr of cosmic time. CAPERS-LRD-z9 exhibits a strong Balmer break, consistent with a central AGN surrounded by dense (∼10¹⁰ cm⁻³) neutral gas. We model CAPERS-LRD-z9 using Cloudy to fit the emission redward of the Balmer break with a dense-gas-enshrouded AGN and bagpipes to fit the rest-ultraviolet emission as a host-galaxy stellar population. This upper limit on the stellar mass of the host galaxy (<10⁹ M⊙) implies that the black hole to stellar mass ratio may be extremely large, possibly >5% (although systematic uncertainties on the black hole mass prevent strong conclusions). However, the shape of the UV continuum differs from typical high-redshift star-forming galaxies, indicating that this UV emission may also be of AGN origin; hence, the true stellar mass of the host may be still lower.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Recommended Citation

Taylor, Anthony J.; Kokorev, Vasily; Kocevski, Dale D.; Akins, Hollis B.; Cullen, Fergus; Dickinson, Mark; Finkelstein, Steven L.; Arrabal Haro, Pablo; Bromm, Volker; Giavalisco, Mauro; Inayoshi, Kohei; Juneau, Stéphanie; Leung, Gene C.K.; Pérez-González, Pablo G.; Somerville, Rachel S.; Trump, Jonathan R.; Amorín, Ricardo O.; Barro, Guillermo; Burgarella, Denis; Brooks, Madisyn; and Carnall, Adam C., "CAPERS-LRD-z9: A Gas-enshrouded Little Red Dot Hosting a Broad-line Active Galactic Nucleus at z = 9.288" (2025). Pacific Faculty Work. 91.
https://scholarlycommons.pacific.edu/all-faculty/91