ALMA Observations of Quasar Host Galaxies at z ~ 4.8

Abstract

We present ALMA Band 7 data of the[CII]lm157.74memission line and underlying far-IR(FIR)continuum for12 luminous quasars atz4.8powered by fast-growing supermassive black holes(SMBHs). Our totalsample consists of 18 quasars, 12 of which are presented here for thefirst time. The new sources consist of sixHerschel/SPIRE-detected systems, which we define as“FIR-bright”sources, and six Herschel/SPIRE-undetectedsystems, which we define as“FIR-faint”sources. We determine dust masses for the quasars hosts of– ́MM0.2 25.0 10dust8, implying interstellar medium gas masses comparable to the dynamical massesderived from the[CII]kinematics. It is found that, on average, the MgIIline is blueshifted by~-500 km s1withrespect to the[CII]emission line, which is also observed when complementing our observations with data from theliterature. Wefind that all of our FIR-bright subsample and most of the FIR-faint objects lie above the main sequenceof star-forming galaxies at~z5. We detect companion submillimeter galaxies for two sources, both FIR-faint, witha range of projected distances of–~20 60kpc and typical velocity shifts of∣∣D-v200 km s1from the quasarhosts. Of our total sample of 18 quasars, 5/18 are found to have dust-obscured star-forming companions.