Abstract
Multi-frequency VLBI observations allow studies of the continuum
spectrum in the different parts of the parsec scale jets of AGN,
providing information on the physical properties of the plasma and
magnetic fields in them. Since VLBI networks cannot be scaled, the range
of spatial frequencies observed differs significantly between the
different observing frequencies, which makes it difficult to obtain a
broadband spectrum of the individual emission features in the jet. In
this paper we discuss a model-fitting based spectral extraction method,
which can significantly relieve this problem. The method uses a priori
knowledge of the source structure, measured at high frequencies, to
allow at lower frequencies the derivation of the sizes and flux
densities of even those emission features that have mutual separations
significantly less than the Rayleigh limit at the given frequency. We
have successfully used this method in the analysis of 5-86 GHz VLBA data
of 3C273. The spectra and sizes of several individual jet features were
measured, thus allowing derivation of the magnetic flux density and the
energy density of the relativistic electrons in the different parts of
the jet. We discuss the results, which include e.g. a detection of a
strong gradient in the magnetic field across the jet of 3C273.
Original language | English |
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Title of host publication | Proceedings of the 9th European VLBI Network Symposium on The role of VLBI in the Golden Age for Radio Astronomy and EVN Users Meeting. Proceedings of Science |
Pages | 9 |
Volume | PoS(IX EVN Symposium) |
Publication status | Published - 2008 |
MoE publication type | B3 Non-refereed conference publication |