Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Interaction of Hydra A jets with the Intracluster medium.  (#203)

Mohammad Ali Nawaz 1 , Geoff Bicknell 1 , Alex Wagner 2
  1. Research School of Astronomy and Astrophysics, ANU, Canberra, ACT, Australia
  2. Center for Computational Sciences, University of Tsukuba, Ibaraki, Japan

We have performed 2D axisymmetric and 3D, relativistic hydrodynamic simulations of the interaction of the Hydra A jets with the cluster environment. The motivation for this study is to model the radio and X-ray structures of the radio galaxy Hydra A and to understand in detail the interaction of radio sources with cooling flows.  

Our basic interpretation of the radio morphology is the following: A disruptive Mach disk at ~6 kpc is responsible for the bright knot between 6-10 kpc in the northern jet. The abrupt transition of the jet to a plume like structure in the northern side is a result of the Mach disk. The gradual transition to turbulence in the southern side is mediated by less disruptive conical shocks. We suggest that the northern jet is highly over-pressured with respect to the environment, because this is a prerequisite for the formation of a Mach disk. Accordingly, the southern jet is less over-pressured. The precession of the jets produces the curved structure and the rotational symmetry of the radio source. 

Using minimum energy estimates and the theory of expanding bubbles we have estimated the kinetic power of the jets to be 6×1044 erg s-1. We have successfully reproduced the inner 50 kpc structures of the Hydra A radio source with our numerical simulations, including the bright knot in the northern jet, the turbulent transition of the jets to plume-like structures, and the curved morphology of the jets. From a parameter space study of the jet power and the jet velocity we obtain a relationship between the position of the Mach disk and the jet velocity. We estimate a jet velocity of ~0.1c from this relationship, which is approximately consistent with other estimates based on Doppler boosting.