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Little Red Dots as Obscured Little Blue Dots: A Super-Eddington Unification Model
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Little Red Dots as Obscured Little Blue Dots: A Super-Eddington Unification Model
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We investigate 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 model the central engine as a geometrically thick, radiation-pressure supported accretion flow whose funnel produces strongly anisotropic, intrinsically blue ionizing continua, coupled to an equatorially concentrated BLR and dusty reprocessing clouds with modest covering factor. Using inclination-dependent spectral energy distributions (SEDs) as input to Cloudy, we show that the extreme broad Halpha EWs of JWST LRDs can be reproduced with global BLR covering factors of only 10%, fully consistent with standard Type~1 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 EUV SED. Weak high-ionization lines (e.g. HeII4686) follow from the orientation-dependent suppression of the XUV/soft X-ray continuum toward equatorial directions, without requiring a fully enclosing gaseous cocoon. Applying a gray dust attenuation law with AV~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 modest global covering factor intercepts and reradiates only a small fraction of the bolometric luminosity, yielding a modest hot-dust bump and far-IR/sub-mm 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 Halpha EW, Balmer decrement, Balmer break, high-ionization line strengths, and IR emission.
Forward citations
Cited by 13 Pith papers
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A Population of Little Red Dot-like Quasars in SDSS
Defines a sample of ~1300 SDSS quasars as Local Red Dots matching LRD photometric colors at z~0.4-0.8, with a V-shaped subset showing Balmer absorption and [NeV] emission, and SEDs modeled as reddened AGN plus host ga...
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Through the Veil: Ly$\alpha$ Illuminates the Host Galaxies of Little Red Dots
Lyα observations of Little Red Dots show luminosities and equivalent widths like normal star-forming galaxies but lower Lyα/Hα ratios and extended asymmetric emission, supporting a two-component model with host-scale gas.
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(LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample
The survey identifies 27 low-redshift LRDs with compact morphology, V-shaped continua, broad Balmer lines with extreme decrements, and ubiquitous outflows, matching high-z counterparts and yielding a number density lo...
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A new sample of Little Red Dots at $z<0.45$ in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability
Eight low-redshift Little Red Dots identified in DESI DR1 exhibit broad Balmer lines, steep decrements, compact shapes, and negligible variability, with a number density roughly 10,000 times lower than at z>4.
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Little Red Dots as Intermediate Mass, Super-Eddington Engines: Insights from Type IIn Supernovae and The 1837-1856 Great Eruption of $\eta$ Carinae
LRDs are reinterpreted as intermediate-mass super-Eddington systems with wind-driven pseudo-photospheres that explain their spectra and imply engine masses below 10^5 solar masses rather than overmassive black holes.
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Little Red Dots as Supermassive Analogs of SS 433
LRDs are interpreted as high-inclination hyper-Eddington accreting SMBHs analogous to SS 433, with V-shaped SEDs, X-ray weakness, and Balmer breaks emerging from disk self-shielding geometry.
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Testing the BH$^*$ Model: a UV-to-Optical Spectral Fitting of The Cliff
Spectral fitting of The Cliff LRD with Bagpipes yields a BH*-like solution with a low-mass metal-poor host, moderate dust, smooth star formation history, and high BH-to-stellar mass ratio.
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Little Red and Blue Dots: AGN-excited narrow lines, Lyman-$\alpha$ emission, and resemblance to standard quasars
JWST data on LRDs and LBDs show AGN-like excitation, strong Lyα with broad components, and X-ray weakness, implying clumpy or equatorial geometries around growing black holes rather than complete gas envelopes.
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Between Degeneracy and Evolution: UV-to-optical Insights into the BH$^*$ Model in Little Red Dots
Bayesian continuum fitting of 66 LRDs shows the BH* model fits ~6% best, rising to ~40% under AGN-disfavoring priors, with most objects stellar/AGN-dominated and possible evolutionary trends.
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The quasi-star model for Little Red Dots: potential and challenges
Quasi-star models using Cloudy radiative transfer reproduce the UV-NIR continuum shape, Balmer break, and hydrogen line luminosities in some LRDs when combined with host galaxy emission, but fail to account for broad ...
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Little red dots as obscured little blue dots: relative abundances, luminosities, and black-hole masses
Little red dots are the dust-reddened, high-inclination counterparts of little blue dots under a super-Eddington unification model, with luminosity-dependent fractions peaking near 20% and obscured systems showing sys...
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Euclid: Scaled-up little red dots and other sources with v-shaped spectral energy distributions at z>4
Euclid identifies 16 massive compact galaxies with V-shaped SEDs at z>4, half as old as the universe at their redshift, mostly distinct from known AGN.
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Non-LTE atmosphere models of very luminous sources and their applicability to Little Red Dots, quasi-stars, and similar objects
Non-LTE wind atmosphere models computed with CMFGEN reproduce the SED and Balmer decrement of most Little Red Dots when dust-attenuated with Av ~2, while predicting Fe II, O I, and Ca lines, but struggle to produce bo...
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