The Abundance of X-Shaped Radio Sources I. VLA Survey of 52 Sources With
  Off-Axis Distortions
  Cheung identified a sample of 100 candidate X-shaped radio galaxies using the
NRAO FIRST survey; these are small-axial-ratio extended radio sources with
off-axis emission. Here we present radio images of 52 of these sources that
have been made from archival Very Large Array data with resolution of about 1
arcsec. Fifty-one of the 52 were observed at 1.4 GHz, seven were observed at
1.4 GHz and 5 GHz, and one was observed only at 5 GHz. We also present overlays
of the SDSS red images for 48 of the sources, and DSS II overlays for the
remainder. Optical counterparts have been identified for most sources, but
there remain a few empty fields. Our higher resolution VLA images along with
FIRST survey images of the sources in the sample reveal that extended
extragalactic radio sources with small axial ratios are largely (60%) cases of
double radio sources with twin lobes that have off-axis extensions, usually
with inversion-symmetric structure. The available radio images indicate that at
most 20% sources might be genuine X-shaped radio sources that could have formed
by a restarting of beams in a new direction following an interruption and axis
flip. The remaining 20% are in neither of these categories. The implications of
this result for the gravitational wave background are discussed in Roberts,
Saripalli, and Subrahmanyan.
