Establish whether red quasars have systematically enhanced accretion or black-hole-to-host mass ratios

Determine whether red quasars at z>6 have higher Eddington ratios or higher M_BH/M_dyn ratios than blue quasars of the same luminosity, using a sample of red quasars with black-hole and host masses measured consistently.

Background

For J1440+0019, the inferred Eddington ratio and position in the black-hole--dynamical-mass plane are indistinguishable from those of high-redshift blue quasars. A possible evolutionary interpretation is that reddening marks a phase in which the black hole grows ahead of its host, but testing that interpretation requires a larger, consistently analyzed sample. At the time of the study, only J1205-0000 and GNz7q provided additional comparison points.

References

If the reddening marks a phase in which the black hole grows ahead of its host, red quasars as a class should sit at higher Eddington ratios or higher M_{\rm BH}/M_{\rm dyn} than blue quasars of the same luminosity. Testing this requires a sample of z>6 red quasars with black-hole and host masses measured in the same way and placed on the same two planes; at present J1205$-$0000 and GNz7q are the only other entries (Sect.~\ref{sec:landscape}).

— A dust-reddened quasar in a [C II]-luminous host at z=6.55  (2610.13758 - Yang et al., 9 Oct 2026) in Section 4.2, “Accretion properties and the black-hole--host mass relation”