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 Hubble Space Telescope 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(4-6) 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 the JWST. Using near-infrared camera imaging at 3.6 and 1.5 mu m and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of 13 x and 3.4 x 10(10) M-circle dot, respectively), compact and disc-like. Near-infrared spectroscopy at medium resolution 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 x 10(9) and 2.0 x 10(8) M-circle dot, 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.

Automated summary

Researchers have successfully captured images of host galaxies of two quasars with redshifts greater than 6 using the Hyper Suprime-Cam camera. The host galaxies are massive disc-like structures and their black hole mass-stellar mass relation is consistent with that observed at lower redshifts. This suggests that the relationship between black holes and their host galaxies was established less than a billion years after the Big Bang.