Preprint typeset using LATEX style emulateapj v. 12/01/06 REDSHIFT 6.4 HOST GALAXIES OF 108 SOLAR MASS BLACK HOLES: LOW STAR FORMATION RATE AND DYNAMICAL MASS

We present ALMA observations of rest-frame far-infrared continuum and [C ii] line emission in two z = 6.4 quasars with black hole masses of ≈ 108M. CFHQS J0210-0456 is detected in the continuum with a 1.2 mm flux of 120 ± 35µJy, whereas CFHQS J2329-0301 is undetected at a similar noise level. J2329-0301 has a star formation rate limit of < 40 M yr−1, considerably below the typical value at all redshifts for this bolometric luminosity. By comparison with hydro simulations, we speculate that this quasar is observed at a relatively rare phase where quasar feedback has effectively shut down star formation in the host galaxy. [C ii] emission is also detected only in J0210-0456. The ratio of [C ii] to far-infrared luminosity is similar to that of low redshift galaxies of comparable luminosity, suggesting the previous finding of an offset in the relationships between this ratio and far-infrared luminosity at low- and high-redshift may be partially due to a selection effect due to the limited sensitivity of previous continuum data. The [C ii] line of J0210-0456 is relatively narrow (FWHM = 189±18 km s−1), indicating a dynamical mass substantially lower than expected from the local black hole – velocity dispersion correlation. The [C ii] line is marginally resolved at 0.′′7 resolution with the blue and red wings spatially offset by 0.′′5 (3 kpc) and a smooth velocity gradient of 100 km s−1 across a scale of 6 kpc, possibly due to rotation of a galaxy-wide disk. These observations are consistent with the idea that stellar mass growth lags black hole accretion for quasars at this epoch with respect to more recent times