2020ApJ...895...74N

We present ALMA Band 7 data of the [C II] λ157.74µm emission line and underlying far-IR (FIR) continuum for 12 luminous quasars at z≃4.8 powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of 18 quasars, 12 of which are presented here for the first time. The new sources consist of six Herschel/SPIRE-detected systems, which we define as "FIR-bright" sources, and six Herschel/SPIRE-undetected systems, which we define as "FIR-faint" sources. We determine dust masses for the quasars hosts of M_dust≤ 0.2–25.0×10⁸M_☉, implying interstellar medium gas masses comparable to the dynamical masses derived from the [C II] kinematics. It is found that, on average, the Mg II line is blueshifted by ∼500kms^–1 with respect to the [C II] emission line, which is also observed when complementing our observations with data from the literature. We find that all of our FIR-bright subsample and most of the FIR-faint objects lie above the main sequence of star-forming galaxies at z∼5. We detect companion submillimeter galaxies for two sources, both FIR-faint, with a range of projected distances of ∼20–60 kpc and typical velocity shifts of |Δv| ≲200 kms^–1 from the quasar hosts. Of our total sample of 18 quasars, 5/18 are found to have dust-obscured star-forming companions.