Volume 394, Number 3, November II 2002
|Page(s)||851 - 861|
|Section||Cosmology (including clusters of galaxies)|
|Published online||21 October 2002|
Connections between millimetre continuum variations and VLBI structure in 27 AGN
Tuorla Observatory, Visl Institute for Space Physics and Astronomy, University of Turku, 21500 Piikki, Finland
2 Metshovi Radio Observatory, Helsinki University of Technology, 02540 Kylml, Finland
3 Department of Physics, University of Turku, 20100 Turku, Finland
4 Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
Corresponding author: T. Savolainen, firstname.lastname@example.org
Accepted: 27 August 2002
We compare total flux density variations in 27 γ-ray blazars with structural changes in their parsec-scale jets using multi-epoch VLBA observations at 22 and 43 GHz together with data from the Metshovi quasar monitoring program at 22 and 37 GHz. There is a clear connection between total flux density outbursts and VLBI components emerging into the jet. For essentially every new moving VLBI component, there is a coincident total flux density flare, with evolution similar to that of the component. Furthermore, extrapolated ejection times of the new VLBI components correspond to the beginnings of associated flares. Our results suggest that it is possible to explain all the radio variations as shocks propagating down the jet. A large fraction of the shocks grow and decay within the innermost few tenths of a milliarcsecond and therefore we see them only as “core flares” in the VLBI images. However, with present data we cannot exclude the possibility that the core itself also brightens (and thus contributes to the flare) as a shock passes through it.
Key words: BL Lacertae objects: general / galaxies: active / galaxies: jets / quasars: general / radio continuum: galaxies / techniques: interferometric
© ESO, 2002
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