ALMA Observations of Quasar Host Galaxies at z ≃ 4.8

We present ALMA Band 7 data of the [C ii] λ 157.74μm 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 ∼ 500 km s^-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 km s^-1 from the quasar hosts. Of our total sample of 18 quasars, 5/18 are found to have dust-obscured star-forming companions.