ALMA Observations of Quasar Host Galaxies at $z\simeq 4.8$

Abstract

We present ALMA band-7 data of the [CII] $\lambda 157.74\hat{I}¼\mathrm{m}$ emission line and underlying far-infrared (FIR) continuum for twelve luminous quasars at $z\simeq 4.8$, powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of eighteen quasars, twelve of which are presented here for the first time. The new sources consists 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 $M_{dust}\le 0.2-25.0\times 10^8{M}_{\odot }$, implying ISM gas masses comparable to the dynamical masses derived from the [CII] kinematics. It is found that on average the MgII line is blueshifted by $\sim 500{\mathrm{km}\mathrm{s}}^{-1}$ with respect to the [CII] 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 $z\sim 5$. We detect companion sub-millimeter galaxies (SMGs) for two sources, both FIR-faint, with a range of projected distances of $\sim 20-60$ kpc and with typical velocity shifts of $\left|\hat{I}”v\right|\lesssim 200{\mathrm{km}\mathrm{s}}^{-1}$ from the quasar hosts. Of our total sample of eighteen quasars, 5/18 are found to have dust obscured starforming companions.

26 pages, 10 figures, 6 tables. Submitted after Referee acceptance