Astronomy and Astrophysics· 2026Q1
Little red dots as obscured little blue dots: A super-Eddington unification model
- 3citations
- Q1SCImago
- 2026year
Short summary
A new model unifies 'little red dots' (LRDs) and 'little blue dots' (LBDs) by proposing LRDs are dust-reddened, high-inclination views of super-Eddington accreting AGNs, explaining their extreme Balmer emission line strengths.
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Key points
- LRDs are modeled as high-inclination views of super-Eddington accreting AGNs, unifying them with LBDs.
- Extreme Balmer EWs in LRDs are explained by self-shadowing suppressing the optical continuum at high inclinations.
- The model requires a modest BLR covering factor (≃0.1) and explains suppressed high-ionization lines without a gaseous cocoon.
- Dust attenuation (A_V≃3) along LRD sightlines reproduces V-shaped UV-optical continua and large Balmer decrements.
AI-generated from the title and abstract; the full text is not read.
Abstract
We investigated whether little red dots (LRDs) are the dust-reddened, high-inclination counterparts of compact, blue broad-line AGNs (``little blue dots''; LBDs) powered by super-Eddington accretion. We modeled the central engine as a geometrically thick, radiation-pressure supported accretion flow whose funnel produces strongly anisotropic, intrinsically blue ionizing continua. This is coupled to an equatorially concentrated broad-line region (BLR) and dusty reprocessing clouds with a modest covering factor. Using inclination-dependent spectral energy distributions (SEDs) as input to , we show that the extreme broad Hα equivalent widths (EWs) of JWST LRDs can be reproduced with global BLR covering factors of only C_ Cloudy ̊m BLR ≃ 0.1, fully consistent with standard type 1 active galactic nuclei (AGNs) and far below unity. Large Balmer EWs arise because self-shadowing suppresses the high-inclination optical continuum while the BLR is illuminated by an ionizing-rich extreme ultraviolet (EUV) SED. Weak high-ionization lines (e.g., He ,łambda4686) follow from the orientation-dependent suppression of the hard extreme ultraviolet (XUV) and soft X-ray continuum toward equatorial directions, without requiring a fully enclosing gaseous ``cocoon.'' Applying a gray dust attenuation law with A_V≃ 3 along high-inclination (LRD-selected) sightlines, our fiducial model reproduces the V-shaped UV--optical continua of LRDs and the large Balmer decrements. Strong Balmer breaks arise only along the most obscured sightlines. A compact equatorial dust structure with a modest global covering factor intercepts and reradiates only a small fraction of the bolometric luminosity, yielding a modest hot-dust bump and far-infrared and submillimeter output consistent with current measurements and limits and implying small dust masses. This single-framework model links LRD and LBD observables through orientation, predicting correlated trends in Hα EW, Balmer decrement, Balmer break, high-ionization line strengths, and infrared emission. ii
The authors' abstract, as published at the source. Astronomy and Astrophysics, 2026 · DOI ↗
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Field: Astronomy and Astrophysics
Astronomy and AstrophysicsPhysics and Astronomy