@article{22960,
  abstract     = {We construct and characterize a sample of 146 little red dots (LRDs) across 2.0<z<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 µm, with typical T ∼ 5000 K (λpeak ∼ 0.65 µm) 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 λpeak < 0.65 µm typically have strong Balmer breaks, redder UV slopes, and high optical luminosities;
other LRDs show weak or no Balmer breaks, and wide variety in βUV 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 i λ8446, 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.},
  author       = {de Graaff, Anna and Hviding, Raphael E and Naidu, Rohan P and Greene, Jenny E and Miller, Tim B and Leja, Joel and Matthee, Jorryt J and Brammer, Gabriel and Katz, Harley and Bezanson, Rachel and Boogaard, Leindert A and Bose, Sownak and Chisholm, John and Cleri, Nikko J and Dayal, Pratika and Feldmann, Robert and Fudamoto, Yoshinobu and Fujimoto, Seiji and Furtak, Lukas J and Glazebrook, Karl and Gottumukkala, Rashmi and Heintz, Kasper E and Kokorev, Vasily and Labbe, Ivo and Maseda, Michael V and McConachie, Ian and Nanayakkara, Themiya and Nelson, Erica and Nowaczyk, Przemysław and Oesch, Pascal A and Rix, Hans-Walter and Setton, David J and Torralba Torregrosa, Alberto and Walter, Fabian and Wang, Bingjie and Weibel, Andrea and van der Wel, Arjen},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {3},
  publisher    = {Oxford University Press},
  title        = {{Little red dots host black hole stars: A unified family of gas-reddened AGN revealed by JWST/NIRSpec spectroscopy}},
  doi          = {10.1093/mnras/stag1567},
  volume       = {551},
  year         = {2026},
}