The powerful radio galaxy Cygnus A

This image is a radio map (at a wavelength of 22cm) of the powerful radio galaxy Cygnus A, produced from observations at the Very Large Array by John Conway and Philip Blanco in March 1994. The 2 x 1 arcminute image shows Cygnus A's famous double radio lobes, spanning over 500,000 light years, which are fed by jets of energetic particles beamed from the compact radio core between them. The giant lobes are formed when these jets are slowed down by the tenous gas which exists between galaxies. Believed to be the source of power for these jets, the radio core itself is situated at the center of a faint dust-lane elliptical galaxy (GIF) which was first identified in 1952 by Walter Baade and Rudolph Minkowski using the giant 200-inch reflector at Mount Palomar Observatory in San Diego County, California.

Cygnus A was named by radio astronomers after the constellation in which it appears, Cygnus the Swan. Its position (J2000.0) is 19h59m28.355s, +40d44m01.89s (1993 ApJ 402, 546). Despite its great distance from us (600 million light years away), it is still by far the closest powerful radio galaxy and one of the brightest radio sources in the sky.

As such, Cygnus A has always been a popular target for observations right across the electromagnetic spectrum. More recently, Cygnus A has become the subject of renewed interest from astrophysicists who are exploring the relation between powerful radio galaxies and the the much more luminous quasi-stellar radio sources (``quasars'').

For more information about Cygnus A:

• H I absorption in Cygnus A - more results and images from our 1994 observations at the VLA.
• A 6cm image from the VLA, at 0.5 arcsec resolution (courtesy of Chris Carilli). Note that the radio core is more prominent at this shorter wavelength.
• Infrared spectroscopy of Cygnus A - implications for the obscured active nucleus.
  Ward, M. J., Blanco, P. R., Wilson, A. S. & Nishida, M. Ap.J.382, 115.
  (From my PhD thesis) this paper showed the first detection of neutral gas (molecular hydrogen) in Cygnus A, and the first detection of [Si VI] in a radio galaxy.
• X-ray evidence for a buried quasar in Cygnus A by Keith Arnaud
• An atlas of 3C Double Radio Active Galactic Nuclei (DRAGNs) - an excellent compendium of information and images for other powerful radio galaxies
• Other astronomers' radio galaxy image galleries: Greg Taylor's Alan Bridle's

Center for Astrophysics & Space Sciences

Last updated 1997 February 7 by Philip Blanco