350 μm dust emission from high-redshift quasars

We report detections of six high-redshift (1: 8 <= z <= 6: 4), optically luminous, radio-quiet quasars at 350 mu m, using the SHARC II bolometer camera at the Caltech Submillimeter Observatory. Our observations double the number of high-redshift quasars for which 350 mu m photometry is available. By combining the 350 mu m measurements with observations at other submillimeter/millimeter wavelengths, for each source we have determined the temperature of the emitting dust ( ranging from 40 to 60 K) and the far-infrared luminosity [(0.6-2.2) x 10(13) L-circle dot]. The combined mean spectral energy distribution of all high-redshift quasars with two or more rest-frame far-infrared photometric measurements is best fit with a graybody with temperature of 47 +/- 3 K and a dust emissivity power-law spectral index of beta = 1.6 +/- 0.1. This warm dust component is a good tracer of the starburst activity of the quasar host galaxy. The ratio of the far-infrared to radio luminosities of infrared-luminous, radio-quiet high-redshift quasars is consistent with that found for local star-forming galaxies.