A measurement of the Integrated Sachs-Wolfe Effect with the Rapid ASKAP
  Continuum Survey
  The evolution of the gravitational potentials on large scales due to the
accelerated expansion of the Universe is an important and independent probe of
dark energy, known as the integrated Sachs-Wolfe (ISW) effect. We measure this
ISW effect through cross-correlating the cosmic microwave background maps from
the \textit{Planck} satellite with a radio continuum galaxy distribution map
from the recent Rapid ASKAP Continuum Survey (RACS). We detect a positive
cross-correlation at $\sim 2.8\,\sigma$ relative to the null hypothesis of no
correlation. We parameterise the strength of the ISW effect through an
amplitude parameter and find the constraints to be $A_{\mathrm{ISW}} =
0.94^{+0.42}_{-0.41}$, which is consistent with the prediction of an
accelerating universe within the current concordance cosmological model,
$\Lambda$CDM. The credible interval on this parameter is independent of the
different bias models and redshift distributions that were considered when
marginalising over the nuisance parameters. We also detect a power excess in
the galaxy auto-correlation angular power spectrum on large scales ($\ell \leq
40$), and investigate possible systematic causes.
