Simulated relativistic particle transport and nonthermal emission in three-dimensional magnetohydrodynamical models of radio galaxies
We present the first fully three-dimensional magnetohydrodynamical radio galaxy jet models to include explicit acceleration and transport of nonthermal particles. These models allow us to study not only the dynamical behaviors of radio jets, but also the relationship between dynamics and the transport of relativistic electrons. The level of physical detail in the simulations is sufficiently high that we are able to compute extensive sets of “synthetic” radio and X-ray observations of our simulated radio galaxies. These are the first synthetic radio galaxy observations to be compatible with standard astronomical analysis procedures. This work is part of an ongoing effort to understand the dynamical and radiative behavior of radio galaxies. We analyze a suite of simulations of dynamically- identical radio galaxies, designed to help isolate the effects of various particle transport parameters. We find that the cartoon model for radio jets is insufficient for describing sources with strongly broken symmetry. Synchrotron radio surface brightness maps for dynamically-identical models can be markedly different, depending on the dominant transport parameters. Using synthetic observations, we perform two analyses that are commonly used to infer magnetic field values in radio galaxies, and compare the results to the actual simulation data. We find that the method of combining inverse-Compton X-ray and radio synchrotron data to infer field values generally works quite well. Minimum-energy arguments are not nearly as reliable and can be highly misleading. Reanalyzing the standard minimum-energy calculation, we find that serious attempts to use minimum energy must account for the presence of even mild spectral curvature. Synthetic observations are also used to perform an extensive polarimetry analysis of our simulated sources. Our simulations reproduce most of the salient polarization features of real radio galaxies, and very naturally give rise to a so-called “Faraday screen” such as those believed to be responsible for the observed rotation measure behavior of real sources.
- Pub Date:
- November 2002
- Physics: Astronomy and Astrophysics