2015ApJ...801..123W

We present ALMA observations of two moderate-luminosity quasars at redshift 6. These quasars, from the Canada-France High-z Quasar Survey (CFHQS), have black hole masses of ∼ 10⁸M_☉. Both quasars are detected in the [C ii] line and dust continuum. Combining these data with our previous study of two similar CFHQS quasars we investigate the population properties. We show that z > 6 quasars have a significantly lower far-infrared (far-IR) luminosity than bolometric-luminosity-matched samples at lower redshift, inferring a lower star formation rate possibly correlated with lower black hole masses at z = 6. The ratios of [C ii] to far-IR luminosities in the CFHQS quasars are comparable to those of starbursts of similar star formation rate in the local universe. We determine the values of velocity dispersion and dynamical mass for the quasar host galaxies based on the [C ii] data. We find that there is no significant offset from the relations defined by nearby galaxies with similar black hole masses. There is, however, a marked increase in the scatter at z = 6, beyond the large observational uncertainties.