ATCA observations of the MACS-Planck Radio Halo Cluster Project - I. New
  detection of a radio halo in PLCK G285.0-23.7
  We investigate the possible presence of diffuse radio emission in the
intermediate redshift, massive cluster PLCK G285.0-23.7 (z=0.39, M_500 = 8.39 x
10^(14) M_Sun). Our 16cm-band ATCA observations of PLCK G285.0-23.7 allow us to
reach a rms noise level of ~11 microJy/beam on the wide-band (1.1-3.1 GHz),
full-resolution (~5 arcsec) image of the cluster, making it one of the deepest
ATCA images yet published. We also re-image visibilities at lower resolution in
order to achieve a better sensitivity to low-surface-brightness extended radio
sources. We detect one of the lowest luminosity radio halos known at z>0.35,
characterised by a slight offset from the well-studied 1.4 GHz radio power vs.
cluster mass correlation. Similarly to most known radio-loud clusters (i.e.
those hosting diffuse non-thermal sources), PLCK G285.0-23.7 has a disturbed
dynamical state. Our analysis reveals a similarly elongated X-ray and radio
morphology. While the size of the radio halo in PLCK G285.0-23.7 is smaller
than lower redshift radio-loud clusters in the same mass range, it shows a
similar correlation with the cluster virial radius, as expected in the
framework of hierarchical structure formation.
