FAR-INFRARED AND MOLECULAR CO EMISSION FROM THE HOST GALAXIES OF FAINT QUASARS AT z ∼ 6

We present new millimeter and radio observations of nine z similar to 6 quasars discovered in deep optical and near-infrared surveys. We observed the 250 GHz continuum in eight of the nine objects and detected three of them. New 1.4 GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250 GHz detections and detected two of them. Combined with previous millimeter and radio observations, we study the far-infrared (FIR) and radio emission and quasar-host galaxy evolution with a sample of 18 z similar to 6 quasars that are faint at UV and optical wavelengths (rest-frame 1450 angstrom magnitudes of m(1450) >= 20.2). The average FIR-to-active galactic nucleus (AGN) UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z similar to 6 (m(1450) < 20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z similar to 6 quasars, and the average luminosities of samples of submillimeter/millimeter-observed quasars at z similar to 2-5, yields a relationship of L-FIR similar to L-bol(0.62). Five of the 18 faint z similar to 6 quasars have been detected at 250 GHz. These 250 GHz detections, as well as most of the millimeter-detected optically bright z similar to 6 quasars, follow a shallower trend of L-FIR similar to L-bol(0.45) defined by the starburst-AGN systems in local and high-z universe. The millimeter continuum detections in the five objects and molecular CO detections in three of them reveal a few x 10(8) M-circle dot of FIR-emitting warm dust and 10(10) M-circle dot of molecular gas in the quasar host galaxies. All these results argue for massive star formation in the quasar host galaxies, with estimated star formation rates of a few hundred M-circle dot yr(-1). Additionally, the higher FIR-to-AGN luminosity ratio found in these 250 GHz detected faint quasars also suggests a higher ratio between star formation rate and supermassive black hole accretion rate than the UV/optically most luminous quasars at z similar to 6.