An ALMA [C II] Survey of 27 Quasars at z > 5.94

We present a survey of the [C ii] 158 μm line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 quasars using the Atacama Large Millimeter Array (ALMA) at resolution. The [C ii] line was significantly detected (at -σ) in 23 sources (85%). We find typical line luminosities of L_{[C II]}= 10^9-10 L⊙, and an average line width of ∼385 . The [C ii]-to-far-infrared luminosity ratios ([C ii]/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their [C ii] emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 ×10¹⁰ and 2 ×10¹¹ , i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (>3 × 10⁸ M⊙, assuming Eddington-limited accretion). In stacked ALMA [C ii] spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the [C ii] luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.