The case for super-Eddington accretion in JWST broad-line active galactic nuclei during the first billion years

A multitude of studies of data recorded by the James Webb Space Telescope (JWST) reveal a surprising overabundance of over-massive accreting supermassive black holes, leading to a deepening tension between theory and observation for the first billion years of cosmic time. Across X-ray to infrared wavelengths, models built on pre-JWST predictions fail to easily reproduce the observed signatures of active galactic nuclei (or lack thereof), driving uncertainty around the true nature of these sources. Here, using a sample of JWST active galactic nuclei identified via their broadened Hα emission and covered by the deepest X-ray surveys, we find neither any measurable X-ray emission nor any detection of high-ionization emission lines frequently associated with accreting supermassive black holes. We propose that these sources are accreting at or beyond the Eddington limit, which reduces the need for the efficient production of heavy supermassive black hole seeds at cosmic dawn. Using a theoretical model of super-Eddington accretion, we can produce the observed relative dearth of both X-ray and ultraviolet emission, as well as the high Balmer decrements, without the need for substantial dust attenuation. This work indicates that super-Eddington accretion is easily achieved throughout the early Universe, and further study is required to determine what environments are required to trigger this mode of black hole growth. A sample of X-ray-weak active galactic nuclei at high redshift may be accreting above the Eddington limit. This could explain their large masses without the need for heavy supermassive black hole seeds at cosmic dawn.