Katherine Blundell OBE

Abstract:

We present the results of a year-long WSRT monitoring campaign for the quasar J 1819+3845. The extreme variations (regularly 10% per minute) axe explained by interstellar scintillation of a source which is no more that 30 microarrseconds in diameter, with a corresponding brightness temperature of similar to 10(13) K.We use the results of this WSRT campaign to infer critical source parameters (size, structure and lifetime). To first order, the changes in the observed scintillation behaviour over the year are interpreted as being due to a peculiar velocity of the scattering plasma (similar to 20 pc distant), and not due to any changes within the source itself. We discus's the source structure on a size of tens of microarcseconds, and illustrate how such a monitoring campaign can yield such, information.

Abstract:

We do not fully understand the dynamics and evolution of a radio galaxy. Models of classical double (FR II; Fanaroff & Riley 1974) sources are in a reasonable state, but these objects are rare. Non-FRII sources (generically called FRI) axe far more common, but much less well understood. In this paper I use the data to suggest possible new models for FRI sources, and discuss, the physical questions which these new models raise.

Abstract:

Results of recent imaging observations of Virgo A (M 87) are presented. The flow seen in the inner region as the M 87 jet appears to continue out onto much large scales, up to 35 kpc in projection from the cluster core. The energy flux, which supposedly originates in the black hole in the M 87 core, appears. ultimately to be deposited in the hot X-ray gas in the cluster core in the form of heat and work in blowing up two large bubbles. The input energy from the jet currently exceeds the radiative cooling by about a factor of ten or more. This probably transient phenomenon may play an important role in the life history of a cluster core but requires the study of many more examples to understand fully.

Abstract:

A complete sample of 27 radio galaxies was selected from the B2 and 3CR catalogues, in order to study their properties on milliarcsecond scales. In this work we discuss the evidence for high velocity jets in low power radio galaxies and the possible existence of a two velocity jet. structure (fast spine and lower velocity external shear layer).

Abstract:

The shapes of synchrotron spectra contain important information about the origin and evolution of the relativistic electron distributions. The analyses of spectral shapes that appear in the literature are inadequate, at best, to address the important scientific issues. A proper analysis of spectra can illuminate the energy distribution of particles as they are "injected" into diffuse regions, the acceleration and loss processes, the bulk and microscopic transport of electrons and the role of inhomogeneities in the magnetic field. I describe some observational difficulties we face in isolating the actual particle distributions, highlight some of the interpretational "sins" we have committed, and make some modest recommendations.