Rest-frame optical spectra of 3<z<6 QSOs

We extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (AGNs) to the high-luminosity, high-redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100{AA} and H{alpha} AGN luminosities over a wide range of luminosity (10^42^<L_5100_<10^47^ergs/s) or redshift (0<z<6), suggesting that the physical mechanism governing this relation is unchanged from z=0 to 6, over five decades in luminosity.

Similar scaling relations are found between the optical and the UV continuum luminosities or line widths. Applying the scaling relations to the H{beta} black hole (BH) mass (M_BH_) estimator of local AGNs, we derive the M_BH_ estimators based on the H{alpha}, MgII, and CIV lines, finding that the UV-line-based masses are overall consistent with the Balmer-line-based, but with a large intrinsic scatter of 0.40dex for the CIV estimates.