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NATURE OF ACTIVE GALACTIC NUCLEI FROM MASSIVE
INSTANTANEOUS RADIO SPECTRA STUDY WITH
RATAN--600 IN 1997--2006 SUPPLEMENTED BY VLBA
EXPERIMENTS
Yu.A. Kovalev 1 , Y.Y. Kovalev 1,2 , G.V. Zhekanis 3 , N.A. Nizhelsky 3
1 Astro Space Center of Lebedev Physical Institute,
Profsoyuznya 84/32, 117997 Moscow, Russia
2 Max­Planck Institute f˜ur Radioastronomie,
Auf dem H˜ugel 69, 53121 Bonn, Germany
3 Special Astrophysical Observatory of RAS,
Nizhnij Arkhyz, 369167 Russia
ykovalev@avunda.asc.rssi.ru
We present results of observations of 1--22 GHz instantaneous continuum spectra of about
3000 active galactic nuclei performed in 1997--2006 with the 600 meter ring transit radio
telescope RATAN--600. An analysis of types and structure of the measured instantaneous
spectra has lead us to a conclusion that almost all spectra could be modeled as a sum of two
main spectral components: LF­component (decreasing with frequency) and HF­component
(with a maximum in cm­mm band). In the framework of a model with longitudinal magnetic
field, the HF­component is explained by synchrotron radiation of a continuous compact
relativistic jet emerging from the nucleus, the LF­component --- by radiation of optically
thin extended peripheral structures which accumulate jet particles. Long term variability
is studied in about 600 AGNs. It is dominated in the same model by the variable emission
of a compact jet (HF­component) and is explained by variable flow of relativistic particles
injected in the jet base. We also apply another model, a standard homogeneous blob of
relativistic particles with synchrotron self­absorption, for sources with simple parsec scale
structure and peaked spectral shape. On the basis of our combined RATAN and VLBA
measurements, we estimate the magnetic field in jet regions of these sources and compare
it with estimations provided by the model with longitudinal magnetic field.