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Arxiv: GA-NIFS: JWST discovers an offset AGN 740 million years after the Big Bang Published: 12/6/2023 6:29:25 PM Updated: 12/6/2023 6:29:25 PM

Paper abstract: A surprising finding of recent studies is the large number of Active GalacticNuclei (AGN) associated with moderately massive black holes (\rm\log(M_\bullet/M_\odot)~ 6-8), in the first billion years after the BigBang (z>5). In this context, a relevant finding has been the large fractionof candidate dual AGN, both at large separations (several kpc) and in closepairs (less than a kpc), likely in the process of merging. Frequent black holemerging may be a route for black hole growth in the early Universe; however,previous findings are still tentative and indirect. We present JWST/NIRSpec-IFUobservations of a galaxy at z=7.15 in which we find evidence for a \rm\log(M_\bullet/M_\odot)~7.7 accreting black hole, as traced by a broadcomponent of H\beta emission, associated with the Broad Line Region (BLR)around the black hole. This BLR is offset by 620 pc in projection from thecentroid of strong rest-frame optical emission, with a velocity offset of~40 km/s. The latter region is also characterized by (narrow) nebularemission features typical of AGN, hence also likely hosting another accretingblack hole, although obscured (type 2, narrow-line AGN). We exclude that theoffset BLR is associated with Supernovae or massive stars, and we interpretthese results as two black holes in the process of merging. This finding may berelevant for estimates of the rate and properties of gravitational wave signalsfrom the early Universe that will be detected by future observatories likeLISA.