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7th of October 2015
ATNF Colloquium
3D precessing jet simulations for radio galaxy Hydra A
by Mohammad Nawaz (ANU)
We study the structure of an iconic radio source Hydra A focussing on detailed models of the inner 30 kpc of its northern jet. The motivation for this study is to provide a better understanding of the jet energetics, jet velocity, jet composition near its base and provide an interpretation of its complex jet-plume structure. To this end, we have performed a series of 3D relativistic hydrodynamic simulations of dynamical interaction between a precessing jet and the cluster environment. The key features of our model are: i) we identify the inner knots of Hydra A as biconical reconfinement shocks, which are produced when an initially over-pressured jet is collimated by the ambient medium and ii) the curvature of the jet and the jet to plume transition are results of dynamical interaction between a precessing jet and the ICM. Our best fit model, with jet velocity = 0.8c, jet over-pressure ratio = 5, jet density parameter = 13, precession period = 1 Myr and precession angle = 20 degree, reproduces prominent features of the northern jet, for example, i) four bright knots along the jet propagation at approximately correct locations, ii) the turbulent transition of the jet to a plume and iii) the correct curvature of the jet.

Image caption: A comparison between the jet-lobe morphology of the Hydra A northern jet and the best matching simulated jet. Panel (a): Total intensity image of Hydra A at 4635 MHz with 0.6" resolution, reproduced from the original data presented in Taylor et al. (1990). The beam size is shown in the lower left corner. Panel (b): The synthetic total intensity image of the simulated jets with directional parameters, line of sight angle = 42 degr and viewing angle = 45 degr. The length scales shown are projected distances from the core.

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