An Observational and Numerical Study of Extragalactic Radio Sources

by Jeffrey Alan Pedelty

Under the supervision of Professor Lawrence Rudnick


The Very Large Array is used to make radio continuum observations of a sample of 12 distant (z=1) high luminosity 3CR galaxies. Images with arcsecond resolution are produced at the 20cm and 6 cm wavelengths. The total and polarized intensity images are used to create maps of the fractional polarization, depolarization, rotation measure, and spectral index distributions. Additional arcsecond resolution observations at 2 cm wavelength, higher resolution 6 cm and 2 cm wavelength maps, and optical R band continuum and emission-line images of [OII] 3727 wavelength are presented for 3C337. The results show that a galaxy scale, two-phase Faraday medium capable of depolarizing the radio emission exists in the environments of the sample galaxies. The warm phase is observed in emission lines, while the hot gas can presently be seen only through its Faraday effects. Suggestive evidence for dynamically significant interactions between the emission-line gas and the radio sources is presented.
Numerical simulations of the interaction of a Mach 4 relative velocity slip surface with several trains of incident nonlinear sound waves are performed using the Piecewise-Parabolic Method. A resonance in the response of the slip surface to the waves is demonstrated, confirming analytical predictions. Characteristic combinations of nonlinear waves associated with finite kinks which propagate along the slip surface are generated only when the waves are incident at nearly the predicted resonant angle. The width of the resonance decreases as the incident wave strength is reduced.
PPM simulations of the supersonic slip surface between 10:1 density ratio fluids are made at M = 1, 1.9, and 4. Further simulations test the effects of grid resolution, the SLIC interface tracking method, and the initial transverse perturbation. The slip surface has a different characteristic response on either side of the linear stability limit of M = 1.77. Below this limit the slip surface promptly rolls up into large scale vortices. At Mach 4 the evolution is dominated by the propagating kink modes notes above, and the interface is much more stable. Transition behavior is observed at M = 1.9, with neither response dominant. The mass and momentum entrainment efficiencies measured in the simulations decrease with increasing Mach number, and scaling arguments suggest that astrophysically significant amounts of ambient material can be entrained by extragalactic radio sources.