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تسجيل مستخدم جديدPredictions for measuring the 21-cm multi-frequency angular power spectrum using SKA-Low
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Rajesh Mondal
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The light-cone (LC) effect causes the mean as well as the statistical properties of the redshifted 21-cm signal $T_{rm b}(hat{bf n}, u)$ to change with frequency $ u$ (or cosmic time). Consequently, the statistical homogeneity (ergodicity) of the signal along the line of sight (LoS) direction is broken. This is a severe problem particularly during the Epoch of Reionization (EoR) when the mean neutral hydrogen fraction ($bar{x}_{rm HI}$) changes rapidly as the universe evolves. This will also pose complications for large bandwidth observations. These effects imply that the 3D power spectrum $P(k)$ fails to quantify the entire second-order statistics of the signal as it assumes the signal to be ergodic and periodic along the LoS. As a proper alternative to $P(k)$, we use the multi-frequency angular power spectrum (MAPS) ${mathcal C}_{ell}( u_1, u_2)$ which does not assume the signal to be ergodic and periodic along the LoS. Here, we study the prospects for measuring the EoR 21-cm MAPS using future observations with the upcoming SKA-Low. Ignoring any contribution from the foregrounds, we find that the EoR 21-cm MAPS can be measured at a confidence level $ge 5sigma$ at angular scales $ell sim 1300$ for total observation time $t_{rm obs} ge 128,{rm hrs}$ across $sim 44,{rm MHz}$ observational bandwidth. We also quantitatively address the effects of foregrounds on MAPS detectability forecast by avoiding signal contained within the foreground wedge in $(k_perp, k_parallel)$ plane. These results are very relevant for the upcoming large bandwidth EoR experiments as previous predictions were all restricted to individually analyzing the signal over small frequency (or equivalently redshift) intervals.
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