Far-infrared/millimetre emission in 3C sources ^*

Dust in radio galaxies and quasars

¹ Osservatorio Astronomico Padova, Vicolo dell'Osservatorio 5, Padova, 35122, Italy ( Max-Planck–I. für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany) e-mail: andreani@mpe.mpg.de
² Space Telescope – European Coordinating Facility European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany e-mail: rfosbury@eso.org,wfreudli@eso.org
³ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: bemmel@astro.rug.nl

Corresponding author: P. Andreani, andreani@npe.npg.de

Received: 12 April 2001
Accepted: 18 October 2001

Abstract

We present far-infrared and millimetric observations of a sample of 3C objects. Millimetre data were taken at 1.25 mm with the IRAM 30 m antenna feeding the MPIfR bolometer array. Mid-infrared (MIR) and far-infrared (FIR) photometry were carried out with the ISOCAM and ISOPHOT cameras on the ISO Satellite. Additional FIR IRAS observations are also included. We present the entire Spectral Energy Distributions (SEDs) from the UV to radio and discuss the emitting mechanisms. Two composite spectra, one for the radio galaxies and one for the radio quasars, are built in the object rest frame. While the SEDs of the two classes differ, they are indistinguishable in the MIR and FIR range where they probably arise as thermal emission from a dusty torus and a larger-scale (cooler) dust distribution in the host galaxy.