PhD picture, complete with 
silly hat

Martin Hardcastle: thesis abstract

(Submitted for the Ph.D. degree in the University of Cambridge September 1996; approved January 1997. This abstract also appeared in The Observatory 117 251)

I present high-resolution, high-sensitivity images of four FRI radio galaxies and seventeen FRII radio galaxies drawn from the 3CR catalogue, made with the aim of detecting and imaging jets and counterjets.

For the FRIs, I show images of the detailed total intensity and polarization structure in the jets and counterjets and in the sources as a whole. I argue that models in which the jets are initially relativistic but decelerate are a good fit to the overall behaviour of the objects, but that some recent models of the polarization structure are hard to reconcile with the observations [paper]. The radio-optical spectrum of the jet in one object, 3C 66B, is discussed in some detail [paper]. A compact hot spot and FRII-like twin jets are found in the wide-angle-tail object 3C 130 [paper].

For the seventeen FRIIs (part of a complete sample of 21 objects with 0.15 < z < 0.3) I detect new jets or possible jets in a number of objects; there are jets or probable jets in 76% of the sample as a whole. The properties of the hot spots of the objects and their implications for models of radio sources are discussed. I present evidence for continuing collimated outflow from the primary and secondary hot spots [paper].

I use my observations, together with data from previous work, to define an unbiased sample of 50 FRII radio galaxies with z < 0.3, and measure quantities of interest from the maps available to me. Trends in this sample are discussed and compared with those seen in samples of other classes of object, such as powerful quasars. [paper] Using Monte Carlo simulation, I show that the prominences and sidednesses of jets in the sample are consistent with relativistic beaming models, and constrain the velocities required and the efficiency of a typical beam [paper].

Back to my home page, or get PDF (long!) or PostScript montage of FRII radio galaxy pictures.