Global Jet Watch

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.

Abstract:

Being immensely powerful, and hence detectable out to great distances, classical double radio galaxies have long been recognised as cosmological probes of great potential. Before this potential can be realised, it is necessary to understand the physical mechanisms by which these objects evolve and change with time. This chapter describes how to deduce from classical double radio source observables (luminosity, spectral index, redshift and linear size) the essential nature of how these objects evolve and the true relationships between the underlying physical parameters (jet-power, age etc). I discuss the key role played by hotspots in governing the energy distribution of the lobes they feed, and subsequent spectral evolution.

Abstract:

We use numerical simulations to discuss some aspects of the hydrodynamics of radio galaxies, and the affect that hydrodynamical considerations have on the long term evolution of such sources. Using these simulations, we can start to assess the impact that a radio galaxy may have on the energy and entropy budget of its host galaxy or cluster. A full hydrodynamic treatment of radio galaxy expansion is also necessary to interpret correctly the X-ray shells and cavities that, are seen in some sources by ROSAT and Chandra.