Thermal Emission from Warm Dust in the Most Distant Quasars

We report new continuum observations of fourteen z∼6 quasars at 250 GHz and fourteen quasars at 1.4 GHz. We summarize all recent millimeter and radio observations of the sample of the thirty-three quasars known with 5.71 ≤ z ≤ 6.43, and present a study of the rest frame far-infrared (FIR) properties of this sample. These quasars were observed with the Max Plank Millimeter Bolometer Array (MAMBO) at 250 GHz with mJy sensitivity, and 30% of them were detected. We also recover the average 250 GHz flux density of the MAMBO undetected sources at 4σ, by stacking the on-source measurements. The derived mean radio-to-UV spectral energy distributions (SEDs) of the full sample and the 250 GHz non-detections show no significant difference from that of lowerredshift optical quasars. Obvious FIR excesses are seen in the individual SEDs of the strong 250 GHz detections, with FIR-to-radio emission ratios consistent with that of typical star forming galaxies. Most 250 GHz-detected sources follow the LFIR–Lbol relationship derived from a sample of local IR luminous quasars (LIR > 10 L⊙), while the average LFIR/Lbol ratio of the non-detections is consistent with that of the optically-selected PG quasars. The MAMBO detections Department of Astronomy, Peking University, Beijing 100871, China National Radio Astronomy Observatory, PO Box 0, Socorro, NM, USA 87801 Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany Max-Planck-Institute for Astronomy, Königsstuhl 17, 69117 Heidelberg, Germany Max-Planck-Institut für Radioastronomie, Auf dem Hügel 71, 53121 Bonn, Germany Institut d’Astrophysique de Paris, CNRS and Universite Pierre et Marie Curie, Paris, France Institute de Radioastronomie Millimetrique, St. Martin d’Heres, F-38406, France Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA, 08544 Steward Observatory, The University of Arizona, Tucson, AZ 85721 Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802