Sharc-II 350 mu m observations of thermal emission from warm dust in z >= 5 quasars

We present observations of four z >= 5 SDSS quasars at 350 mu m with the SHARC-II bolometer camera on the Caltech Submillimeter Observatory. These are among the deepest observations that have been made by SHARC-II at 350 mu m, and three quasars are detected at >= 3 sigma significance, greatly increasing the sample of 350 mu m (corresponds to rest frame wavelengths of < 60 mu m at z >= 5), detected high-redshift quasars. The derived rest frame far-infrared (FIR) emission in the three detected sources is about five to ten times stronger than that expected from the average spectral energy distribution (SED) of the local quasars given the same 1450 angstrom luminosity. Combining the previous submillimeter and millimeter observations at longer wavelengths, the temperatures of the FIR-emitting warm dust from the three quasar detections are estimated to be in the range of 39-52 K. Additionally, the FIR-to-radio SEDs of the three 350 mu m detections are consistent with the emission from typical star-forming galaxies. The FIR luminosities are similar to 10(13)L(circle dot) and the dust masses are >= 10(8)M(circle dot). These results confirm that huge amounts of warm dust can exist in the host galaxies of optically bright quasars as early as z similar to 6. The universe is so young at these epochs (similar to 1Gyr) that a rapid dust-formation mechanism is required. We estimate the size of the FIR dust-emission region to be about a few kpc, and further provide a comparison of the SEDs among different kinds of dust-emitting sources to investigate the dominant dust-heating mechanism.