Little Red Dots as Intermediate Mass, Super-Eddington Engines: Insights from Type IIn Supernovae and The 1837-1856 Great Eruption of eta Carinae
Rohan P. Naidu, Jorryt Matthee, Anna de Graaff, Alberto Torralba, Chris Ashall, Harley Katz, John Chisholm, Gabriel Brammer, Luc Dessart, Anna-Christina Eilers, Raphael E. Hviding, David O. Jones, Vasily Kokorev, Joel Leja, Hanpu Liu, Zhaoran Liu, Devesh Nandal, Pascal A. Oesch, Conor L. Ransome, Robert A. Simcoe, Wendy Q. Sun, Andrea Weibel, Mengyuan Xiao
astro-ph.GA, astro-ph.CO, astro-ph.HE, astro-ph.SR
Submitted: 2026-06-29
Comments: Submitted to the Open Journal of Astrophysics. Comments warmly welcomed
License: http://creativecommons.org/licenses/by/4.0/
The gist: JWST's Little Red Dots (LRDs) display a unique constellation of features that do not occur simultaneously in any other class of galaxies or AGN.
Terminology
Abstract
JWST's Little Red Dots (LRDs) display a unique constellation of features that do not occur simultaneously in any other class of galaxies or AGN. Here we observe that many of these features find parallels in the 19th century Great Eruption (GE) of eta Carinae and a sub-class of supernovae (Type IIn). Drawing on these stellar phenomena -- outflows trapped by dense circumstellar gas envelopes -- we sketch a possible scenario for LRDs. Outflows from the central engine produce an enshrouding envelope of gas that may be thought of as a slow wind. This dense wind and its enormous extent produce an opacity so high that a pseudo-photosphere forms within the wind, obscuring the central engine and manifesting as a blackbody-like continuum. Radiation from the buried engine powers the system. The engine may also launch fast winds that crash into the existing envelope to generate shocks. Lines form within the wind above the photosphere -- electron scattering and absorption in the clumpy (ionized + neutral) medium account for broad wings and P-Cygni cores. A key implication is that inferences of ``overmassive black holes" may be interpreting this wind-like physics as a virial broad-line region. We propose an escape velocity argument to constrain the mass of the engine, which yields M<10 5 M for the typical LRD. The lack of variability and low surface gravity of the photosphere provide further support for intermediate mass (M about10 3-6 M), but very luminous super-Eddington (L/L 5) systems harboring a supermassive star or intermediate mass black hole. Paralleling the evolution of IIn SNe, dust production in the envelope may mark the beginnings of classical AGN. This paper explores a possible self-consistent explanation for the entire life-cycle of LRDs, from their enshrouding in dense gas to their fates as seeds of massive black holes.
Sources
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- Beyond the Monsters: A More Complete Census of Black Hole Activity at Cosmic Dawn
- Too Quiet for Comfort: Local Little Red Dots Lack Variability over Decades
- Pulsational Instability of Quasi-Stars: Interpreting the Variability of Little Red Dots
- Impact of Resonance, Raman, and Thomson Scattering on Hydrogen Line Formation in Little Red Dots
- Little Red Dots as Globular Clusters in Formation
- JADES Data Release 4 Paper I: Sample Selection, Observing Strategy and Redshifts of the complete spectroscopic sample
- OCEANS of Absorption: High-resolution NIRSpec Spectroscopy Reveals Diverse Balmer-line Absorption in Little Red Dots
- RUBIES: a complete census of the bright and red distant Universe with JWST/NIRSpec
- A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
- Little Red Dots host Black Hole Stars: A unified family of gas-reddened AGN revealed by JWST/NIRSpec spectroscopy
- SN2023ixf: Radiative-transfer modeling of the photospheric phase evolution from the ultraviolet to the infrared
- BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$
- Irony at z=6.68: a bright AGN with forbidden Fe emission and multi-component Balmer absorption
- Simultaneous modeling of FeII emission in the optical and near-infrared in a prototypical Narrow-Line Seyfert 1 galaxy
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