Asymmetries in extragalactic double radio sources: clues from 3D simulations of jet-disc interaction

V. Gaibler, S. Khochfar, M. Krause

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Observational and theoretical studies of extragalactic radio sources have suggested that an
inhomogeneous environment may be responsible for observed arm-length asymmetries of
jets and the properties of extended emission-line regions in high-redshift radio galaxies. We
perform 3D hydrodynamic simulations of the interaction of a powerful extragalactic bipolar
jet with a disc-shaped clumpy interstellar medium (ISM) of lognormal density distribution
and analyse the asymmetry. Furthermore, we compute the relation between jet asymmetry
and the ISM properties by means of Monte Carlo simulations based on a 1D propagation
model for the jet through the dense medium. We find that the properties of the ISM can be
related to a probability distribution of jet arm-length asymmetries: disc density and height are
found to have the largest effect on the asymmetry for realistic parameter ranges, while the
Fourier energy spectrum of the ISM and turbulent Mach number only have a smaller effect.
The hydrodynamic simulations show that asymmetries generally may be even larger than
expected from the 1D model due to the complex interaction of the jet and its bow shock with
gaseous clumps, which goes much beyond simple energy disposal. From our results, observed
asymmetries of medium-sized local radio galaxies may be explained by gas masses of 109–
1010 M in massive elliptical galaxies. Furthermore, the simulations provide a theoretical
basis for the observed correlation that emission-line nebulae are generally found to be brighter
on the side of the shorter lobe in high-redshift radio galaxies. This interaction of jets with the
cold gas phase suggests that star formation in evolving high-redshift galaxies may be affected
considerably by jet activity.
Original languageEnglish
Pages (from-to)155-161
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Early online date21 Jan 2011
Publication statusPublished - 11 Feb 2011


  • hydrodynamics, methods: numerical, ISM: structure, galaxies: ISM, galaxies: jets


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