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 mu-tual 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 21 cm 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 100 h−1 Mpc 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 reioniza-tion process, wherein extended histories result in a much stronger signal compared to instanta-neous 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. Key words: cosmology: theory, cosmic microwave background, large scale structure of uni-verse, diffuse radiation, radio lines: general