Abstract
Considerable asymmetries in jets from active galactic nuclei (AGN) and associated double radio sources can be caused by an inhomogeneous interstellar medium of the host galaxy. These asymmetries can easily be estimated by 1D propagation models, but hydrodynamical simulations have shown that the actual asymmetries can be considerably larger. With a set of smaller-scale hydrodynamical simulations we examine these asymmetries, and find they are typically a factor of ~ 3 larger than in 1D models. We conclude that, at high redshift, large asymmetries in radio sources are expected in gas-rich galaxies with a clumpy interstellar medium.
Highlights
The propagation of jets from active galactic nuclei (AGN) is strongly dependent on the medium they are moving through
Assuming jet propagation according to one-dimensional momentum balance, this method was able to describe the asymmetries in the hydrodynamical simulation to first order, but it was found that considering the full hydrodynamics the actual delay is even larger due to “second order” effects: The blast wave already affects the interstellar medium (ISM) structure, moves and compresses clumps, and changes the density profile that the jet needs to propagate through
Our results show that the simulation of Paper I shows a rather typical asymmetry for the chosen parameters, not an exceptionally large one
Summary
The propagation of jets from active galactic nuclei (AGN) is strongly dependent on the medium they are moving through. In contrast to the blast waves, the propagation of the two jet beams depends on the inertia of obstructing ambient matter and any asymmetry in the stochastically located clumps results in an asymmetry of the radio source.[11,8,1,13,5,10] Once both jets have broken out of the ISM, they will propagate more efficiently in the diffuse ambient gas but still keep an imprint of this initial asymmetry, which can be regarded as a propagation delay between both jets for the large-scale propagation. Assuming jet propagation according to one-dimensional momentum balance, this method was able to describe the asymmetries in the hydrodynamical simulation to first order, but it was found that considering the full hydrodynamics the actual delay is even larger due to “second order” effects: The blast wave already affects the ISM structure, moves and compresses clumps, and changes the density profile that the jet needs to propagate through. It is important to keep in mind that the asymmetries discussed here are only due to asymmetries in the ISM, while in actual radio sources observed asymmetries may be caused by ambient gas asymmetries on larger scales[5] or other effects,[4] including light travel times,[12] Doppler boosting[15] and intrinsic instabilities of the jet beam.[9]
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