Bent Double Radio Sources from the FIRST Survey

As a double-lobed radio source passes through a cluster of galaxies, the drag of the intracluster medium on the radio plasma gives the lobes a swept-back or "bent" appearance. Thus, bent doubles can signal the presence of a cluster. Many nearby clusters have bent double radio sources; the Coma cluster has 2 and Abell 119 has 4.

Here are some example bent double radio sources from the FIRST Survey:

Click on the image to see all 384 radio sources in our present sample.

In imaging and spectroscopic followup of about 100 bent double fields, we have found clusters to z = 0.84.

The source numbered 256 above is in this rich cluster, at z=0.64. From Keck spectroscopy of 10 galaxies in this field, we derive a velocity dispersion of 1000 km/s, comparable to the Coma cluster.

Our collaboration is beginning a systematic imaging survey of 80 bent doubles which have NO optical counterparts on the Digitized Sky Survey. The hope is that these radio sources mark the locations of distant clusters (z > 1).

Although bent doubles do not occur in all clusters, they are an unbiased tracer of large scale structure and are relatively immune to the selection effects of optical and X-ray searches. The FIRST Survey will ultimately cover 10,000 sq. degrees centered on the north Galactic cap; by searching for clusters and density enhancements using bent doubles, it will be possible to map structures on extremely large scales and over great distances.

Jump To:
UCD Physics Dept.
Cosmology Research Group
Institute of Geophysics and Planetary Physics at the Lawrence Livermore National Laboratory

Modified February, 2003
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