Jets, hotspots and lobes: what X-ray observations tell us about extragalactic radio sources

Abstract

The brightest and most numerous discrete radio sources in the sky, radio galaxies and quasars, are powered by twin jets of plasma which emerge at relativistic speeds from very small regions at the centre of large elliptical galaxies, powered by mass infall on to supermassive black holes. The jets can carry material out to very large distances (millions of light years) where it forms balloon-like lobes. Until recently it has been impossible to make definite statements about the energy or the nature of the matter supplied by the jets, or the dynamics of the lobes as they expand into the external medium. This has meant that crucial questions about the generation of radio sources and their effect on their environment have gone unanswered. The situation has been revolutionized by the launch at the start of this decade of a new generation of X-ray observatories, Chandra and XMM-Newton. In this article, I explain why observations with these instruments have made such a difference, what we have learned as a result and why the community remains divided on some important features of the interpretation of the data.

Active Galactic Nucleus Interaction With the Hot Gas Environment: Understanding From the Radio and X-Ray Data

“…Cygnus A, while undetected at optical wavelengths, radiate significantly in the X-ray (Wilson et al, 2000), which is interpreted as evidence that some hotspots emit X-rays by a synchrotron self-Compton process. Finally, extended X-ray emission from the radio lobes of powerful, FR II radio galaxies and quasars is thought to be produced by inverse-Compton scattering off the CMB (Feigelson et al, 1995;Hardcastle et al, 2002aHardcastle et al, , 2005.…”

Emerging frontiers in the physical sciences

“…The survey will yield knowledge about the actual distribution of baryons and may serve to confirm our understanding of the Big Bang theory. The third paper in this group by Hardcastle (2005) presents an interesting discussion on some striking energetic astronomical sources observable through X-rays.…”

Future perspectives in astronomy and the earth sciences

“…The survey will yield knowledge about the actual distribution of baryons and may serve to confirm our understanding of the Big Bang theory. The third paper in this group, by Hardcastle (2005) presents an interesting discussion on some striking energetic astronomical sources observable through X-rays. Some cautionary remarks are made on the use of the observational instruments and the interpretation of data.…”