Cross-correlation of the H i 21-cm signal and Lyα forest: a probe of cosmology

Abstract

Separating the cosmological redshifted 21-cm signal from foregrounds is a major challenge. We present the cross-correlation of the redshifted 21-cm emission from neutral hydrogen (H i) in the post-reionization era with the Lyα forest as a new probe of the large-scale matter distribution in the redshift range z= 2–3 without the problem of foreground contamination. Though the 21-cm and the Lyα forest signals originate from different astrophysical systems, they are both expected to trace the underlying dark matter distribution on large scales. The multifrequency angular cross-correlation power spectrum estimator is found to be unaffected by the discrete quasar sampling, which only affects the noise in the estimate.