A high black hole to host mass ratio in a lensed AGN in the early Universe.

Early JWST observations have uncovered a new population of red sources that might represent a previously overlooked phase of supermassive black hole growth 1--3 . One of the most intriguing examples is an extremely red, point-like object that was found to be triply-imaged by the strong lensing (SL) cluster Abell 2744 4 . Here we present deep JWST/NIRSpec observations of this object, Abell2744-QSO1. The spectroscopy confirms that the three images are of the same object, and that it is a highly reddened (A V  ≃ 3) broad emission line Active Galactic Nucleus (AGN) at a redshift of z spec  = 7.0451 ± 0.0005. From the width of Hβ ([Formula: see text]) we derive a black hole mass of [Formula: see text]. We infer a very high ratio of black hole to galaxy mass of at least 3 %, an order of magnitude more than is seen in local galaxies 5 , and possibly as high as 100 %. The lack of strong metal lines in the spectrum together with the high bolometric luminosity ([Formula: see text]) indicate that we are seeing the black hole in a phase of rapid growth, accreting at 30 % of the Eddington limit. The rapid growth and high black hole to galaxy mass ratio of A2744-QSO1 suggest that it may represent the missing link between black hole seeds 6 and the first luminous quasars 7 .