Reconstructing the radial velocity profile of cosmic voids with
  kinematic Sunyaev-Zeldovich Effect
  We develop an estimator to extract the mean radial velocity profile of cosmic
voids via the kinematic Sunyaev-Zeldovich effect of pairs of galaxies
surrounding them. The estimator is tested with simulated pure kSZ map and void
catalogue data from the same simulation. The results show that the recovered
signal could be attenuated by low angular resolution of the map or large
aperture photometry filter radius size, but the mean radial velocity profile
can be fully recovered with our estimator. By applying the estimator to the
Planck 2D-ILC CMB map, with galaxy and void catalogues from BOSS DR12, we find
that the estimated void velocity profile is $3.31\sigma$ apart from null
detection for for voids with continuously rising density profiles asymptoting
to the mean density; and $1.75\sigma$ for voids with positive density contrast
shell surrounded. By fitting the reconstructed data to the theoretical profile,
we find the reduced $\chi^{2}$ to be $1.19$ and $0.62$ for the two types of
void, respectively, indicating a good fit of the model to the data. We then
forecast the detectability of the radial velocity profile of cosmic voids with
future CMB surveys, including SPT-3G, AdvACT, and Simons Observatory. We find
that the contamination effect from CMB residuals is negligible with survey area
over $2,000~{\rm deg}^2$, especially with aperture photometry size less than
$1\,{\rm arcmin}$. But the effect from instrumental noise is non-negligible.
For future SPT-3G, AdvACT and Simons Observatory, the detection is potentially
achievable from $3\sigma$ to $10\sigma$ C.L., depending on specific
instrumental parameters. This opens a new window of probing dynamics of the
cosmic structures from the kinematic Sunyaev-Zeldovich effect.
