Extracting the late-time kinetic Sunyaev-Zel'dovich effect
  We propose a novel technique to separate the late-time, post-reionization
component of the kinetic Sunyaev-Zeldovich (kSZ) effect from the contribution
to it from a (poorly understood and probably patchy) reionization history. The
kSZ effect is one of the most promising probe of the {\em missing baryons} in
the Universe. We study the possibility of reconstructing it in three dimensions
(3D), using future spectroscopic surveys such as the Euclid survey. By
reconstructing a 3D template from galaxy density and peculiar velocity fields
from spectroscopic surveys we cross-correlate the estimator against CMB maps.
The resulting cross-correlation can help us to map out the kSZ contribution to
CMB in 3D as a function of redshift thereby extending previous results which
use tomographic reconstruction. This allows the separation of the late time
effect from the contribution owing to reionization. By construction, it avoids
contamination from foregrounds, primary CMB, tSZ effect as well as from star
forming galaxies. Due to a high number density of galaxies the signal-to-noise
(S/N) for such cross-correlational studies are higher, compared to the studies
involving CMB power spectrum analysis. Using a spherical Bessel-Fourier (sFB)
transform we introduce a pair of 3D power-spectra: ${\cal
C}^{\parallel}_\ell(k)$ and ${\cal C}^{\perp}_\ell(k)$ that can be used for
this purpose. We find that in a future spectroscopic survey with near all-sky
coverage and a survey depth of $z\approx 1$, reconstruction of ${\cal
C}^{\perp}_\ell(k)$ can be achieved in a few radial wave bands
$k\approx(0.01-0.5 h^{-1}\rm Mpc)$ with a S/N of upto ${\cal O}(10)$ for
angular harmonics in the range $\ell=(200-2000)$ (abrdiged).
