Little Red Dots Modeled as Off-Axis Super-Eddington SMBH Fountain Flows Producing Balmer Cocoons

The paper uses spherically symmetric marginally unbound wind profiles fed into the Sirocco radiative transfer code to show how trapped radiation inflates a quasi-spherical envelope around the inner disk. At outflow rates of 5-15 solar masses per year this produces Compton-thick regions where Lyman-alpha trapping sustains n=2 populations, enabling Balmer breaks at lower densities than LTE models require. Spectra match the progression from little blue dots to red LRDs with full breaks.

This off-axis geometry resolves the tension between observed slow absorption troughs and the fast winds expected from super-Eddington flows, which escape only near the poles. The photon-tired fountain flow allows fallback material to sustain the envelope, a mechanism also relevant to supermassive stars. Prior JWST LRD studies focused on stellar or dust interpretations and missed these radiative-transfer signatures.

The model synthesizes the Kaaz preprint with earlier super-Eddington wind theory from Jiang et al. 2019 and observed LRD demographics in Matthee et al. 2024. It predicts that edge-on sightlines dominate the population while polar views appear as unobscured quasars.

Future multi-epoch NIRSpec observations can test whether P Cygni variability tracks the predicted 2.5-15 solar mass per year outflow range, tightening constraints on early black hole growth channels.