SHARC-II 350 μm Observations of Thermal Emission from Warm Dust in z >= 5 Quasars

We present observations of four z >= 5 SDSS quasars at 350 μm 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 μm, and three quasars are detected at >=3σ significance, greatly increasing the sample of 350 μm (corresponds to rest frame wavelengths of <60 μm 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 Å 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 μm detections are consistent with the emission from typical star-forming galaxies. The FIR luminosities are ~10¹³ L _sun and the dust masses are >=10⁸ M _sun. These results confirm that huge amounts of warm dust can exist in the host galaxies of optically bright quasars as early as z ~ 6. The universe is so young at these epochs (~1 Gyr) 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.