Cross-correlation Study between the Cosmological 21-cm Signal and the
  kinetic Sunyaev-Zel'dovich effect
  The Universe's Epoch of Reionization (EoR) can be studied using a number of
observational probes that provide complementary or corroborating information.
Each of these probes suffers from its own systematic and statistical
uncertainties. It is therefore useful to consider the mutual information that
these data sets contain. In this paper we present a cross-correlation study
between the kinetic Sunyaev-Zel'dovich effect (kSZ) -- produced by the
scattering of CMB photons off free electrons produced during the reionization
process -- and the cosmological 21cm signal -- which reflects the neutral
hydrogen content of the Universe, as a function of redshift. The study is
carried out using a simulated reionization history in 100Mpc/h scale N-body
simulations with radiative transfer. In essence we find that the two probes
anti-correlate. The significance of the anti-correlation signal depends on the
extent of the reionization process, wherein extended histories result in a much
stronger signal compared to instantaneous cases. Unfortunately however, once
the primary CMB fluctuations are included into our simulation they serve as a
source of large correlated noise that renders the cross-correlation signal
insignificant, regardless of the reionization scenario.
