Peer-reviewedCC BYMonthly Notices of the Royal Astronomical Society
Little red dots host black hole stars: a unified family of gas-reddened AGN revealed by JWST /NIRSpec spectroscopy
30 affiliations
- 1Center for Astrophysics | Harvard & Smithsonian , 60 Garden St., Cambridge, MA 02138 ,
- 2Max-Planck-Institut für Astronomie , Königstuhl 17, D-69117, Heidelberg ,
- 3MIT Kavli Institute for Astrophysics and Space Research , 70 Vassar Street, Cambridge, MA 02139 ,
- 4Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544 ,
- 5Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Ave, Evanston, IL 60201 ,
- 6Department of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802 ,
- 7Institute for Computational & Data Sciences, The Pennsylvania State University , University Park, PA 16802 ,
- 8Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802 ,
- 9Institute of Science and Technology Austria (ISTA) , Am Campus 1, A-3400 Klosterneuburg ,
- 10Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen , Jagtvej 128, København N, DK-2200 ,
- 11Department of Astronomy & Astrophysics, University of Chicago , 5640 S. Ellis Avenue, Chicago, IL 60637 ,
- 12Kavli Institute for Cosmological Physics, University of Chicago , Chicago, IL 60637 ,
- 13Department of Physics and Astronomy and PITT PACC, University of Pittsburgh , Pittsburgh, PA 15260 ,
- 14Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,
- 15Institute for Computational Cosmology, Department of Physics, Durham University , South Road, Durham DH1 3LE ,
- 16Cosmic Frontier Center, The University of Texas at Austin , Austin, TX 78712 ,
- 17Department of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712 ,
- 18Canadian Institute for Theoretical Astrophysics , University of Toronto, 60 St George St, Toronto, ON M5S 3H8 ,
- 19David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto , 50 St George St, Toronto, ON M5S 3H4 ,
- 20Department of Physics , University of Toronto, 60 St George St, Toronto, ON M5S 3H8 ,
- 21Department of Astrophysics, University of Zurich , Zurich CH-8057 ,
- 22Center for Frontier Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 ,
- 23Dunlap Institute for Astronomy and Astrophysics , 50 St. George Street, Toronto, ON M5S 3H4 ,
- 24Centre for Astrophysics and Supercomputing, Swinburne University of Technology , Melbourne, VIC 3122 ,
- 25Department of Astronomy, University of Geneva , Chemin Pegasi 51, CH-1290 Versoix ,
- 26Department of Astronomy, University of Wisconsin-Madison , 475 N. Charter St., Madison, WI 53706 ,
- 27Department for Astrophysical and Planetary Science, University of Colorado , Boulder, CO 80309 ,
- 28Astronomical Observatory Institute, Faculty of Physics and Astronomy, Adam Mickiewicz University , ul. Słoneczna 36, PL-60-286, Poznań ,
- 29California Institute of Technology , Pasadena, CA 91125 ,
- 30Sterrenkundig Observatorium, Universiteit Gent , Krijgslaan 281 S9, B-9000 Gent ,
Abstract
We construct and characterize a sample of 146 little red dots (LRDs) across 2.0lt zlt 9.3, selecting all sources with v-shaped ultraviolet (UV)–optical continua from James Webb Space Telescope (JWST) NIRSpec/PRISM spectra and compact morphologies in NIRCam/F444W imaging. We show that LRD continuum spectra are well described by modified blackbodies across ∼ 0.4−1.0 μ m, with typical T∼ 5000 K (λ peak∼ 0.65 μ m) across 2 dex in luminosity, and a tail toward T∼ 2000 K. LRDs therefore trace a locus in the Hertzsprung–Russell diagram that is analogous to stars on the Hayashi track, strongly supporting the picture that LRDs are active galactic nucleus (AGN) embedded in optically thick dense gas envelopes. Hotter LRDs with λ peaklt 0.65 μ m typically have strong Balmer breaks, redder UV slopes, and high optical luminosities; other LRDs show weak or no Balmer breaks, and wide variety in β UV and L5100. Crucially, we demonstrate that the UV–optical continua are strongly linked to the Hα, Hβ, [O iii], and O i line properties. There is a tight linear relation between the Hα and optical continuum luminosities, as well as Hα and O small I λ 8446, indicating that Balmer, O i, and optical emission must primarily be powered by the same source. The Balmer decrement increases strongly toward higher LHα , L5100, and Balmer break strength, providing key evidence for luminosity-dependent effects of collisional (de-)excitation and resonant scattering in the gaseous envelopes. In contrast, we show that [O iii] emission likely originates from star-forming host galaxies, with strong variation in the AGN-to-host ratio among the LRD population. Our work presents an empirical description of the nature and structure of LRDs, defining a new benchmark for ongoing LRD model developments.
Related
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- The THRILS Factor: Investigating the properties of Little Red Dots (LRDs) at 3<z<6 with JWST/NIRSpec
- From “The Cliff” to “Virgil”: Mapping the Spectral Diversity of Little Red Dots with JWST/NIRSpec
- A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curve
BibTeX
@article{graaff2026little,
title = {{Little red dots host black hole stars: a unified family of gas-reddened AGN revealed by JWST /NIRSpec spectroscopy}},
author = {Anna de Graaff and Raphael E Hviding and Rohan P. Naidu and Jenny E Greene and Tim B Miller and Joel Leja and Jorryt Matthee and Gabriel Brammer and Harley Katz and Rachel Bezanson and Leindert A Boogaard and Sownak Bose and John Chisholm and Nikko J. Cleri and Pratika Dayal and Robert Feldmann and Yoshinobu Fudamoto and Seiji Fujimoto and Lukas J. Furtak and Karl Glazebrook and Rashmi Gottumukkala and Kasper E Heintz and Vasily Kokorev and Ivo Labbe and Michael V Maseda and Ian McConachie and Themiya Nanayakkara and Erica Nelson and Przemysław Nowaczyk and Pascal A. Oesch and Hans-Walter Rix and David J. Setton and Alberto Torralba and Fabian Walter and Bingjie Wang and Andrea Weibel and Arjen van der Wel},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = aug,
doi = {10.1093/mnras/stag1567},
url = {https://doi.org/10.1093/mnras/stag1567},
note = {CC BY},
}
RIS
TY - JOUR
TI - Little red dots host black hole stars: a unified family of gas-reddened AGN revealed by JWST /NIRSpec spectroscopy
AU - Anna de Graaff
AU - Raphael E Hviding
AU - Rohan P. Naidu
AU - Jenny E Greene
AU - Tim B Miller
AU - Joel Leja
AU - Jorryt Matthee
AU - Gabriel Brammer
AU - Harley Katz
AU - Rachel Bezanson
AU - Leindert A Boogaard
AU - Sownak Bose
AU - John Chisholm
AU - Nikko J. Cleri
AU - Pratika Dayal
AU - Robert Feldmann
AU - Yoshinobu Fudamoto
AU - Seiji Fujimoto
AU - Lukas J. Furtak
AU - Karl Glazebrook
AU - Rashmi Gottumukkala
AU - Kasper E Heintz
AU - Vasily Kokorev
AU - Ivo Labbe
AU - Michael V Maseda
AU - Ian McConachie
AU - Themiya Nanayakkara
AU - Erica Nelson
AU - Przemysław Nowaczyk
AU - Pascal A. Oesch
AU - Hans-Walter Rix
AU - David J. Setton
AU - Alberto Torralba
AU - Fabian Walter
AU - Bingjie Wang
AU - Andrea Weibel
AU - Arjen van der Wel
PY - 2026
DA - 2026/08/21
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1567
UR - https://doi.org/10.1093/mnras/stag1567
AB - We construct and characterize a sample of 146 little red dots (LRDs) across 2.0lt zlt 9.3, selecting all sources with v-shaped ultraviolet (UV)–optical continua from James Webb Space Telescope (JWST) NIRSpec/PRISM spectra and compact morphologies in NIRCam/F444W imaging. We show that LRD continuum spectra are well described by modified blackbodies across ∼ 0.4−1.0 μ m, with typical T∼ 5000 K (λ _peak∼ 0.65 μ m) across 2 dex in luminosity, and a tail toward T∼ 2000 K. LRDs therefore trace a locus in the Hertzsprung–Russell diagram that is analogous to stars on the Hayashi track, strongly supporting the picture that LRDs are active galactic nucleus (AGN) embedded in optically thick dense gas envelopes. Hotter LRDs with λ _peaklt 0.65 μ m typically have strong Balmer breaks, redder UV slopes, and high optical luminosities; other LRDs show weak or no Balmer breaks, and wide variety in β _UV and L_5100. Crucially, we demonstrate that the UV–optical continua are strongly linked to the Hα, Hβ, [O iii], and O i line properties. There is a tight linear relation between the Hα and optical continuum luminosities, as well as Hα and O small I _ λ 8446, indicating that Balmer, O i, and optical emission must primarily be powered by the same source. The Balmer decrement increases strongly toward higher L_Hα , L_5100, and Balmer break strength, providing key evidence for luminosity-dependent effects of collisional (de-)excitation and resonant scattering in the gaseous envelopes. In contrast, we show that [O iii] emission likely originates from star-forming host galaxies, with strong variation in the AGN-to-host ratio among the LRD population. Our work presents an empirical description of the nature and structure of LRDs, defining a new benchmark for ongoing LRD model developments.
SN - 0035-8711
SN - 1365-2966
SN - 1365-8711
ER -