Fisher matrix predictions for detecting the cosmological 21 cm signal with the Ooty Wide Field Array (OWFA)

Abstract

We have used the Fisher matrix formalism to quantify the prospects of detecting the z = 3.35 redshifted 21-cm HI power spectrum with the upcoming radio-imterferometric array OWFA. OWFA's frequency and baseline coverage spans comoving Fourier modes (k) in the range 0.018 to 2.7 [1/Mpc]. The OWFA HI signal, however, is predominantly from the range k below 0.2 [1/Mpc]. The larger modes, though abundant, do not contribute much to the HI signal. In this work we have focused on combining the entire signal to achieve a detection. We find that a 5-sigma detection of A_{HI} is possible with ~ 150 hr of observations, here A^2 _{HI} is the amplitude of the HI power spectrum. We have also carried out a joint analysis for A_{HI} and the redshift space distortion parameter. Our study shows that OWFA is very sensitive to the amplitude of the HI power spectrum. However, the anisotropic distribution of the k modes does not make it very suitable for measuring the redshift space distortion parameter.