2026/02/25 by Piero Madau, Roberto Maiolino
#astro-ph.GA #astro-ph.HE
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.