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Astron. Astrophys. 334, 799-804 (1998)

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Nature of 60µm emission in 3C 47, 3C 207 and 3C 334

Ilse M. van Bemmel 1, Peter D. Barthel 1 and Min S. Yun 2

1 Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
2 NRAO VLA, P.O. Box 0, Socorro, NM, USA

Received 2 February 1998 / Accepted 16 March 1998


We try to explain the unusually high far-infrared emission seen by IRAS in the double-lobed radio-loud quasars 3C 47, 3C 207 and 3C 334. High resolution cm-mm observations were carried out to determine their radio core spectra, which are subsequently extrapolated to the far-infrared in order to determine the strength of the synchrotron far-infrared emission. The extrapolated flux densities being considerably lower than the observed values, a significant nonthermal far-infrared component is unlikely in the case of 3C 47 and 3C 334. However, this component could be responsible for the far-infrared brightness of 3C 207. Our analysis demonstrates that nonthermal emission cannot readily account for the difference between quasars and radio galaxies in the amount of their far-infrared luminosity. On the other hand, a significant role for this mechanism is likely; full sampling of the mm-submm spectral energy distributions is needed to address the issue quantitatively.

Key words: infrared: galaxies – radio continuum: galaxies – quasars: general – quasars: individual: 3C 47; 3C 207; 3C 334

Send offprint requests to: Ilse M. van Bemmel

© European Southern Observatory (ESO) 1998

Online publication: June 2, 1998