Cross-correlation of the HI 21-cm Signal and Lyman-alpha Forest: A Probe Of Cosmology

Understand

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 (HI) in the post-reionization era with the Ly-alpha forest as a new probe of the large scale matter distribution in the redshift range z=2 to 3 without the problem of foreground contamination.
• Though the 21-cm and the Ly-alpha forest signals originate from different astrophysical systems, they are both expected to trace the underlying dark matter distribution on large scales.
• The multi-frequency angular cross-correlation power spectrum estimator is found to be unaffected by the discrete quasar sampling, which only affects the noise in the estimate.