Likelihood of extreme environments required for red LRD spectra under sustained super-Eddington accretion

Ascertain the likelihood, in the early Universe, of either high dust attenuation or extremely dense gas environments forming around supermassive black holes undergoing sustained super-Eddington accretion, at levels sufficient to produce the observed red spectra and strong Balmer breaks characteristic of Little Red Dots.

Background

To reproduce the extremely red spectra and strong Balmer breaks observed in LRDs like CAPERS-LRD-z9 and MoM-BH* within the authors’ models, two environmental scenarios are invoked: substantial dust attenuation or an AGN embedded in very dense gas. These conditions can amplify the AGN’s contribution and mimic spectral breaks typically associated with stellar populations.

While the spectral fits demonstrate plausibility, the authors emphasize uncertainty in how often such extreme environments arise, especially if sustained super-Eddington accretion is required. Quantifying their occurrence is necessary to evaluate whether these scenarios can broadly explain the LRD population.