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Astron. Astrophys. 362, 75-96 (2000)

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

M. Polletta 1,2, T.J.-L. Courvoisier 1,2, E.J. Hooper 3 and B.J. Wilkes 3

1 Geneva Observatory, Ch. des Maillettes 11, 1290 Sauverny, Switzerland
2 Integral Science Data Centre, Ch. d'Ecogia 16, 1290 Versoix, Switzerland
3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA

Received 15 March 2000 / Accepted 16 May 2000


Continuum observations at radio, millimetre, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large observational datasets provided by ISOPHOT on board the Infrared Space Observatory, by the IRAM interferometer, 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 it is difficult to separate it from the bright non-thermal component. The dust is predominantly heated by the optical/ultraviolet radiation emitted from the external components of the AGN. A starburst contributes to the IR emission at different levels, but always less than the AGN ([FORMULA] 27%). The distribution of temperatures, sizes, masses, and luminosities of the emitting dust are independent of the quasar type.

Key words: galaxies: quasars: general – infrared: galaxies – radio continuum: galaxies

Table 3-Table 6, Fig. 1 and Fig. 4 are only available electronically here with the On-Line publication.

Send offprint requests to: Maria.Polletta@obs.unige.ch

© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100