Pulsars, transients and relativistic astrophysics

Abstract:

Abell 3667 is a rich X-ray luminous southern cluster of galaxies at a redshift of 0.055. The properties of this cluster suggest that it is probably in a post-merger state. Recent radio observations taken with the Australia Telescope Compact Array (ATCA) have allowed a detailed investigation of the environment in this cluster. We present here a synopsis of these observations.

Abstract:

We present a sample of bright compact sources with peaked radio spectra. The sample is likely to contain a mixture of a number of very young radio sources and some beamed objects whose radio emission is dominated by a single component. Flux density Variability is common among these sources, which we call "High Frequency Peakers" (HFPs).

Abstract:

Using ROSA T observations, we estimate gas pressures in the X-ray-emitting media surrounding 63 FR II radio galaxies and quasars. We compare these pressures with the internal pressures of the radio-emitting plasma estimated by assuming minimum energy or equipartition. The majority of the radio sources (including 12/13 sources with modelled, spatially resolved X-ray emission) Appear to be underpressured with respect to the external medium, suggesting that simple minimum-energy arguments underestimate the sources' internal energy densities. Some consequences of this result are discussed.