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Astron. Astrophys. 354, 497-503 (2000)

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VLBI observations of 3C 273 at 22 GHz and 43 GHz

II. Test of synchrotron self-Compton process

F. Mantovani 1, W. Junor 2, I.M. McHardy 3 and C. Valerio 1

1 Istituto di Radioastronomia del CNR, via Gobetti 101, 40129 Bologna, Italy
2 Institute for Astrophysics, University of New Mexico, Albuquerque, NM, USA
3 Department of Physics and Astronomy, University of Southampton, UK

Received 25 June 1999 / Accepted 23 November 1999


The VLBI observations at 22 GHz and 43 GHz of the quasar 3C 273 obtained during a multi-frequency campaign in late 1992 in the radio, millimetre and X-ray bands allow us to derive the components' angular sizes, their peak fluxes and turnover frequencies. Lower limits to the Doppler factors have been derived by comparing the observed X-ray fluxes with those predicted by the Synchrotron Self-Compton model. Independent estimates of the Doppler factors were obtained through the assumption of the energy equipartition between the particles and the magnetic field. Of the five components used to model the first two milli-arcseconds of the jet, apart from the core, two components are in equipartition and the remaining two, at larger distances from the core, have large Doppler factors and are mainly responsible for the X-ray emission due to the Synchrotron Self-Compton process.

Key words: radiation mechanisms: non-thermal – techniques: interferometric – galaxies: jets – galaxies: quasars: general – galaxies: quasars: individual: 3C 273 – radio continuum: galaxies

Send offprint requests to: fmantovani@ira.bo.cnr.it

© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000