Gas-drenched black hole at cosmic dawn hints at rapid early growth
New JWST observations reveal MoM-BH*-1, a z≈7.76 source with an extreme Balmer break, broad Hβ emission, and strong Balmer absorption best explained by a supermassive black hole enshrouded in an extremely dense, nearly dust-free gas envelope. The envelope (nH ~10^11 cm−3, NH ~10^25.8 cm−2, turbulence ~500 km/s) produces a UV-weak, Balmer-break-dominated spectral energy distribution with little host-galaxy light, suggesting possible super-Eddington accretion. This implies rapid black-hole growth in the early universe and cautions that Balmer-line widths under such conditions may overestimate BH masses by up to ~2 dex; the host is a faint, low-mass dwarf galaxy. The finding links to the broader population of “little red dots” and challenges conventional SMBH growth models at cosmic dawn.
