Probing supervoids with weak lensing
  The cosmic microwave background (CMB) has non-Gaussian features in the
temperature fluctuations. An anomalous cold spot surrounded with a hot ring,
called the Cold Spot is one of such features. If a large underdence region
(supervoid) resides towards the Cold Spot, we would be able to detect a
systematic shape distortion in the images of background source galaxies via
weak lensing effect. In order to estimate the detectability of such signals, we
used the data of $N$-body simulations to simulate full-sky ray-tracing of
source galaxies. We searched for a most prominent underdense region using the
simulated convergence maps smoothed at a scale of 20 degree and obtained
tangential shears around it. The lensing signal expected in a concordant
$\Lambda$CDM model can be detected at a signal-to-noise ratio $S/N\sim3$. If a
supervoid with a radius of $\sim 200\,h^{-1}\,\textrm{Mpc}$ and a density
contrast $\delta_0 \sim -0.3$ at the centre resides at a redshift $z\sim 0.2$,
on-going and near-future weak gravitational lensing surveys would detect a
lensing signal with $S/N\gtrsim4$ without resorting to stacking. From the
tangential shear profile, we can obtain a constraint on the projected mass
distribution of the supervoid.
