Constraining warm dark matter power spectrum using the cross-correlation of HI 21 cm signal and the Lyman-α forest
We have considered the prospects for measuring the cross Warm Dark Matter (WDM) power spectrum of the redshifted HI 21-cm signal and the Lyman-α forest and thereby constraining WDM mass using observations with upcoming radio-interferometers—the Ooty Wide Field Array (OWFA) and SKA1-mid, and a spectroscopic survey of the quasars. We have considered a quasar survey with a mean observed quasar number density of n̄Q = 48 deg−2 over a collecting area of 14455 deg2, and a mean spectroscopic SNR = 5. Our analysis with OWFA shows that it is possible to measure the WDM power spectrum in several k-bins at k ⩽ 0.45 Mpc−1 with SNR > 5 using observations of 200 hours each in 100 different fields-of-view for mWDM = 0.25 keV . Considering the possibility of the joint measurement of the parameters, the warm dark matter density parameter ΩWDM, and the dark energy density parameter ΩΛ0, we find that the relative error on the 1−σ measurement of the parameter ΩWDM is ∼ 0.8 for a fiducial mWDM = 0.25 keV . However, we find that OWFA is not sensitive towards measuring the suppression of the WDM power spectrum, and therefore, cannot be used to constrain the WDM mass. Considering the analysis with SKA I mid, we find that for a fiducial mWDM= 0.25 keV, the suppression in the cross power spectrum can be measured at ∼ 10 − σ around k ∼ 0.2 Mpc−1 for a total observing time of 20000 hours distributed uniformly over 50 independent pointings where we have binned the available k-range as Δ k = k/5.