Exploiting the 21cm power spectrum: constraints on the warm dark matter and cross-correlation with the Lyman-alpha forest flux

The LCDM model experiences small scale problems that could be solved by allowing dark matter to have intrinsic thermal velocities, i.e. warm dark matter (WDM). In this talk I discuss the impact of WDM on the 21cm power spectrum, by means of high resolution hydrodynamical N-body simulations of different dark matter (DM) scenarios and different models of neutral hydrogen (HI) spatial distribution. I forecast the bounds that the Square Kilometre Array (SKA) will place on the DM particle mass. A major drawback of the 21cm observations is foreground contamination, expected to be orders of magnitudes higher than the signal. To address this problem, I propose to cross-correlate the Lyman-alpha forest with the 21cm maps. I show how the two fields are completely anti-correlated on large scales and I use the anisotropy of the power spectra in redshift-space to determine the values of the bias parameters of both fields. My results point out that linear theory is capable of reproducing the shape and amplitude of the cross-power up to rather non-linear scales. Finally, I show how the 21cm-Lya cross-power spectrum can be detected by combining data from a BOSS-like survey together with 21cm intensity mapping observations by SKA1-MID with a S/N ratio higher than 3 in k range of [0.06, 1] h/Mpc.