Dust Budget Crisis in Little Red Dots

Abstract Little red dots (LRDs), a population of active galactic nuclei (AGNs) recently identified by JWST, are characterized by their compact morphology and red optical continuum emission, which is often interpreted as evidence for significant dust extinction of A V ≳ 3 mag. However, the dust-reddened AGN scenario is increasingly challenged by their faint near-to-far-infrared emission and a potential “dust budget crisis” in cases when the host galaxy is either undetectably low-mass or absent. In this study, we reevaluate the dust extinction level in LRDs by modeling the UV-to-infrared spectra for various extinction laws and a broad range of dusty distribution parameters. Comparing the predicted infrared fluxes with observational data from JWST MIRI, Herschel, and the Atacama Large Millimeter/submillimeter Array, our analysis finds that the visual extinction is tightly and consistently constrained to A V ≲ 1.0–1.5 mag for A2744–45924, RUBIES-BLAGN-1, and stacked spectral energy distributions from a large sample of LRDs under the SMC extinction law, with slightly weaker constraints for those with gray extinction in the UV range. The revised A V values yield radiative efficiencies of ∼10% for the LRD population, easing the tension with the Sołtan argument for the bulk AGN population at lower redshifts. Moreover, this moderate extinction (or dust-free) scenario, with reprocessed emission spectra testable by future far-infrared observatories, provides a paradigm shift in understanding the natures, environments, and evolutionary pathways of massive black holes in the early Universe.