EDP Sciences
Free access
Volume 456, Number 2, September III 2006
Page(s) 493 - 504
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20065310

A&A 456, 493-504 (2006)
DOI: 10.1051/0004-6361:20065310

The role of Kelvin-Helmholtz instability in the internal structure of relativistic outflows. The case of the jet in 3C 273

M. Perucho1, 2, A. P. Lobanov2, J.-M. Martí1 and P. E. Hardee3

1  Departament d'Astronomia i Astrofísica, Universitat de València, C/Dr. Moliner 50, 46100 Burjassot, Spain
2  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: perucho@mpifr-bonn.mpg.de
3  Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA

(Received 29 March 2006 / Accepted 15 May 2006)

Context.Relativistic outflows represent one of the best-suited tools to probe the physics of AGN. Numerical modelling of internal structure of the relativistic outflows on parsec scales provides important clues about the conditions and dynamics of the material in the immediate vicinity of the central black holes in AGN.
Aims.We investigate possible causes of the structural patterns and regularities observed in the parsec-scale jet of the well-known quasar 3C 273.
Methods.We present here the results from a 3D relativistic hydrodynamics numerical simulation based on the parameters given for the jet by Lobanov & Zensus (2001, Science, 294, 128), and one in which the effects of jet precession and the injection of discrete components have been taken into account. We compare the model with the structures observed in 3C 273 using very long baseline interferometry and constrain the basic properties of the flow.
Results.We find growing perturbation modes in the simulation with similar wavelengths to those observed, but with a different set of wave speeds and mode identification. If the observed longest helical structure is produced by the precession of the flow, longer precession periods should be expected.
Conclusions.Our results show that some of the observed structures could be explained by growing Kelvin-Helmholtz instabilities in a slow moving region of the jet. However, we point towards possible errors in the mode identification that show the need of more complete linear analysis in order to interpret the observations. We conclude that, with the given viewing angle, superluminal components and jet precession cannot explain the observed structures.

Key words: galaxies: quasars: individual: 3C 273 -- galaxies: active -- galaxies: jets -- hydrodynamics

© ESO 2006