An Objective Survey of Mpc-Scale Radio Emission in 0.03<z<0.3 Bright
  X-ray Clusters
  We have performed the the first census of Mpc-scale radio emission to include
control fields and quantifiable upper limits for bright X-ray clusters in the
range 0.03<z<0.3 . Through reprocessing radio images from the WENSS survey, we
detect diffuse emission from approximately 30% of the sample. We find a
correlation similar to the well-studied relationship between radio halo and
X-ray luminosities of the host cluster, but also find that large scale radio
galaxy detections follow a similar trend to that for radio halos. With this
quantitative study, we thus confirm the upper envelope to the radio
luminosities for X-ray selected clusters, and the higher detection rates for
diffuse radio emission (including halos, relics and radio galaxies) at X-ray
luminosities above approximately 10**45 erg/s. We can neither confirm nor
refute the claims for a tight correlation between these radio halo and X-ray
luminosities, i.e. whether the halo luminosity function of X-ray clusters is
bimodal (having high/on and low/off states), or whether the radio luminosity
can take on a wide range of values up to a maximum at each cluster X-ray
luminosity. The resolution of this issue may provide a unique diagnostic for
the timescales over which relativistic particles can be accelerated following
cluster mergers. We discuss several important selection effects on radio vs.
X-ray luminosity correlations, including surface brightness thresholds and
non-X-ray-selected diffuse radio sources. We also report several new detections
of diffuse emission, including a Mpc-scale relic in RXJ1053.7+5450, a possible
halo/relic combination in Abell 2061, a serendipitous diffuse X-ray source
associated with poor clusters in the Abell 781 field, and confirmation of very
weak diffuse emission patches outside of Abell~2255.
