Millimeter and Radio Observations ofz~ 6 Quasars

We present millimeter and radio observations of 13 SDSS quasars at redshifts z ∼ 6. We observed 11 of them with the Max Planck Millimeter Bolometer Array (MAMBO-2) at the IRAM 30 m telescope at 250 GHz and all of them with the Very Large Array (VLA) at 1.4 GHz. Four sources are detected by MAMBO-2 and six are detected by the VLA at the ≳3 σ level. These sources, together with another six published in previous papers, yield a submillimeter/millimeter- and radio-observed SDSS quasar sample at z ∼ 6. We use this sample to investigate the far-infrared (FIR) and radio properties of optically bright quasars in the early universe. We compare this sample to lower redshift samples of quasars observed in the submillimeter and millimeter wavelengths (sub)mm and find that the distribution of the FIR-to- B -band optical luminosity ratio ( L FIR / L B ) is similar from z ∼ 2 to 6. We find a weak correlation between the FIR luminosity ( L FIR ) and B -band optical luminosity ( L B ) by including the (sub)mm observed samples at all redshifts. Some strong (sub)mm detections in the z ∼ 6 sample have radio-to-FIR ratios within the range defined by star-forming galaxies, which suggests possible coeval star-forming activity with the powerful AGN in these sources. We calculate the rest-frame radio-to-optical ratios ( R = L ν,1.4 GHz / L ν,4400 Å ) for all of the VLA-observed sources in the z ∼ 6 quasar sample. Only one radio detection in this sample, J083643.85+005453.3, has R ∼ 40 and can be considered radio-loud. There are no strong radio sources ( R ≥ 100) among these SDSS quasars at z ∼ 6. These data are consistent with, although do not set strong constraints on, a decreasing radio-loud quasar fraction with increasing redshift.