Comparison of Radio Observations and Numerical Simulations of the Radio Lobes of Cygnus A

Abstract

We present a comparison of radio observations of the archetypal powerful radio galaxy Cygnus A and 2-D numerical hydrodynamical simulations. We characterize some global trends in the observed radio properties and compare them with the properties of a simulated radio source. The numerical results are the following. Jets propagating in a constant density atmosphere will decelerate with time. Thus, the estimated dynamical age of the source will be greater than the actual age of the source. For a source similar to Cygnus A the difference will be about a factor of 2. The second moment gives an accurate representation of the "true" width of the simulated source. The Gaussian FWHM tends to be about 40% larger than the true width and can be systematically in error if the surface brightness exhibits multiple peaks. We suggest that the ratio of the Gaussian FWHM to the second moment may be a diagnostic of the emissivity profile in the lobes. The simulations can qualitatively reproduce the overall observed morphology and the behavior of the cross-sections in surface brightness, the decline in surface brightness with distance from the hot spots, and the width of the lobes. This suggests that the 2-D simulations give a reasonable representation of the properties of Cygnus A.

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Cited by in corpus (6)

• The Fermi Bubbles. II. The Potential Roles of Viscosity and Cosmic Ray Diffusion in Jet Models
• On the Importance of Very-light Internally-subsonic AGN Jets in Radio-mode AGN Feedback
• Self-consistent evolution of gas and cosmic rays in Cygnus A and similar FR II classic double radio sources
• Dynamics Inside the Radio and X-ray Cluster Cavities of Cygnus A and Similar FRII Sources
• A Detailed Study of the Lobes of Eleven Powerful Radio Galaxies
• First Dynamic Computation of Synchrotron Emission from the Cygnus A Radio Cavity; Evidence for Electron Pair Plasma in Cavity