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Astron. Astrophys. 345, 769-777 (1999)

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Synchrotron spectra and ages of compact steep spectrum radio sources

M. Murgia 1,2, C. Fanti 1,3, R. Fanti 1,3, L. Gregorini 1,3, U. Klein 4, K.-H. Mack 1,4 and M. Vigotti 1

1 Istituto di Radioastronomia del CNR, Via Gobetti 101, I-40129 Bologna, Italy
2 Dipartimento di Astronomia, Università di Bologna, Via Zamboni 33, I-40126 Bologna, Italy
3 Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, I-40126 Bologna, Italy
4 Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany

Received 7 January 1999 / Accepted 12 March 1999

Abstract

The high-frequency integrated spectra of Compact Steep Spectrum (CSS) sources show breaks with a moderate spectral steepening well fitted by continuous injection synchrotron spectra. In lobe-dominated CSS sources the radiative ages deduced by the synchrotron theory are in the range of up to [FORMULA] years, if equipartition magnetic fields are assumed. These radiative ages are well correlated with the source size indicating that the CSS sources are young . In order to maintain the frustration scenario , in which the sources' lifetimes are [FORMULA] years, their equipartition magnetic field would be systematically decreased by a factor [FORMULA]. To complete the sample used in this work, we conducted observations at 230 GHz with the IRAM 30-m telescope of those sources which did not have such high-frequency observations up to now.

Key words: radiation mechanisms: non-thermal – radio continuum: galaxies

Send offprint requests to: M. Murgia

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© European Southern Observatory (ESO) 1999

Online publication: April 28, 1999
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