ISO continuum observations of quasars at z=1-4. I. Spectral energy distributions of quasars from the UV to far-infrared

Abstract

Eight luminous quasars with -30 < M_B < -27 at z = 1.4-3.7 have been observed in the mid- and far-infrared using ISO. All the quasars have been detected in the mid-infrared bands of ISOCAM, while no far-infrared detections have been made with ISOPHOT. SEDs (Spectral Energy Distributions) from the UV to far-infrared have been obtained while supplementing ISO observations with photometry in the optical and near-infrared made from the ground within 17 months. The SEDs are compared with the MED (Mean spectral Energy Distributions) of low-redshift quasars with -27 < M_B < -22. It is shown that our far-infrared observations were limited by confusion noise due to crowded sources. The observations reported here were made with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands, and the UK) and with the participation of ISAS and NASA, and with the facilities at the Cerro Tololo Inter-american Observatory (CTIO), NOAO, which is operated by AURA, Inc., under contract with NSF, at the Kiso Observatory, which is operated by Institute of Astronomy, the University of Tokyo, and at the Okayama Astrophysical Observatory, the National Astronomical Observatory of Japan.