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.