The cross-correlation between 21cm intensity mapping maps and the Lyman-alpha forest in the post-reionization era

Understand

We investigate the cross-correlation signal between 21cm intensity mapping maps and the Lyman-alpha forest in the fully non-linear regime using state-of-the-art hydrodynamic simulations.

• The cross-correlation signal between these fields can provide a coherent and comprehensive picture of the neutral hydrogen (HI) content of our Universe in the post-reionization era, probing both its mass content and volume distribution.
• We compute the auto-power spectra of both fields together with their cross-power spectrum at z = 2.4 and find that on large scales the fields are completely anti-correlated.
• This anti-correlation arises because regions with high (low) 21cm emission, such as those with a large (low) concentration of damped Lyman-alpha systems, will show up as regions with low (high) transmitted flux.