Detection of stellar light from quasar host galaxies at redshifts above 6.

The detection of starlight from the host galaxies of quasars during the reionization epoch (z > 6) has been elusive, even with deep HST observations 1,2 . The current highest redshift quasar host detected 3 , at z = 4.5, required the magnifying effect of a foreground lensing galaxy. Low-luminosity quasars 4,5,6 from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) 7 mitigate the challenge of detecting their underlying, previously-undetected host galaxies. Here we report rest-frame optical images and spectroscopy of two HSC-SSP quasars at z > 6 with JWST. Using NIRCam imaging at 3.6μm and 1.5μm and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of 13 × and 3.4 × 10 10 M ⊙ , respectively), compact, and disk-like. NIRSpec medium-resolution spectroscopy shows stellar absorption lines in the more massive quasar, confirming the detection of the host. Velocity-broadened gas in the vicinity of these quasars enables measurements of their black hole masses (1.4 × 10 9 and 2.0 × 10 8 M ⊙ , respectively). Their location in the black hole mass - stellar mass plane is consistent with the distribution at low redshift, suggesting that the relation between black holes and their host galaxies was already in place less than a billion years after the Big Bang.