The Jets in Radio Galaxies

Abstract

This thesis describes two studies of extragalactic radio sources at high resolution and sensitivity. Most of the well-known facts about radio sources come from low-resolution imaging, despite the fact that much of the interesting physics (that of the jets and hotspots) occurs on scales that are small compared to the overall source size. This thesis is an attempt to redress the balance and to extract some physical information on the energy transport in these sources from their small-scale radio structure. In this chapter I introduce extragalactic radio sources and briefly describe the current state of knowledge about them and the physics we might hope to extract from observations. In chapter 2 the instruments and techniques used to image sources with the required sensitivity and resolution are described. Chapter 3 is concerned with observations of a small ‘representative’ sample of FRI sources. The features seen in the radio structures of the jets are discussed and used to estimate the physical parameters in the beams. I compare the structures seen in the jets with existing models. In chapter 4 I describe observations of a large sample of FRII sources, and discuss some trends in the features observed. In chapter 5, techniques are developed for extracting quantitative information from the resulting images and from data from previous work by others, and the results are tabulated. In chapter 6 I use these results to try to constrain some physical parameters of the sources. The conclusions of the whole thesis are summed up in chapter 7