The far-infrared emission of radio loud and radio quiet quasars

Continuum observations at radio, millimetre, infrared and soft X-ray energi es are presented for a sample of 22 quasars, consisting of flat and steep s pectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the ra dio and IR energy domains are studied using large observational datasets pr ovided by ISOPHOT on board the Infrared Space Observatory, by the IRAM inte rferometer, by the sub-millimetre array SCUBA on JCMT, and by the European Southern Observatory (ESO) facilities IRAC1 on the 2.2 m telescope and SEST . The spectral energy distributions of all quasars from radio to IR energies are analyzed and modeled with non-thermal and thermal spectral. components. The dominant mechanism emitting in the far/mid-IR is thermal dust emission in all quasars, with the exception of flat spectrum radio loud quasars for which the presence of thermal IR emission remains rather uncertain, since i t is difficult to separate it from the bright non-thermal component. The du st is predominantly heated by the optical/ultraviolet radiation emitted fro m the external components of the AGN. A starburst contributes to the IR emi ssion at different levels, but always less than the AGN (less than or equal to 27%). The distribution of temperatures, sizes, masses, and luminosities of the emitting dust are independent of the quasar type.