Low(er) frequency follow-up of 28 candidate, large-scale synchrotron
  sources
  We follow up on a report by Vacca et al. (2018) of 28 candidate large-scale
diffuse synchrotron sources in an 8{\deg}$\times$8{\deg} area of the sky
(centred at RA 5h0m0s Dec 5{\deg}48'0''). These sources were originally
observed at 1.4 GHz using a combination of the single-dish Sardinia Radio
Telescope (SRT) and archival NRAO VLA Sky Survey (NVSS) data. They are in an
area with nine massive galaxy clusters at z $\approx$ 0.1, and are candidates
for the first detection of filaments of the synchrotron cosmic web. We attempt
to verify these candidate sources with lower frequency observations at 154 MHz
with the Murchison Widefield Array (MWA) and at 887 MHz with the Australian
Square Kilometre Array Pathfinder (ASKAP). We use a novel technique to
calculate the surface brightness sensitivity of these instruments to show that
our lower frequency observations, and in particular those by ASKAP, are ideally
suited to detect large-scale, extended synchrotron emission. Nonetheless, we
are forced to conclude that none of these sources are likely to be synchrotron
in origin or associated with the cosmic web.
