A gas-enshrouded and gas-reddened black hole at cosmic dawn

Key Points:

• MoM-BH*-1, observed with JWST's NIRSpec, is a unique high-redshift (z ≈ 7.76) source exhibiting an extraordinarily strong Balmer break (strength ~7.7), far exceeding theoretical limits for stellar populations, indicating its spectrum does not arise from stars but from a supermassive black hole (SMBH) embedded in extremely dense gas.
• The source shows broad Hβ emission and deep, broad Balmer absorption lines implying gas densities >10^9 cm^−3, a point-source morphology (<100 pc), and tentative variability (~30% brightening over 56 days), consistent with an SMBH enshrouded in a dense, turbulent, Compton-thick gas envelope with negligible dust attenuation.
• Cloudy spectral synthesis modeling suggests MoM-BH*-1’s features arise from an AGN accretion disk embedded within extremely dense (n_H ~10^11 cm^−3), turbulent gas (velocity ~500 km/s), producing the strong Balmer break and absorption without requiring significant dust, challenging previous models that invoked heavy dust obscuration.
• The SMBH mass is estimated to be around 10^6–10^7 solar masses, potentially undergoing super-Eddington accretion, while the faint host galaxy is a low-mass dwarf (stellar mass <10^8.5 solar masses), possibly metal-poor and located near a more massive galaxy, supporting theories of direct collapse BH formation influenced by environmental factors.
• MoM-BH*-1 serves as a template for explaining the enigmatic "little red dots" (LRDs) population observed by JWST, reconciling their puzzling spectral properties as a composite of a dense-gas-enshrouded AGN dominating the rest-optical and a star-forming galaxy dominating the UV, with implications for SMBH growth and feedback in the early universe.