Speaker
Description
The light-cone (LC) effect arises from the cosmological evolution of the redshifted 21-cm signal along an observer’s line of sight (LoS), which is the frequency axis. It is particularly pronounced during the Epoch of Reionization (EoR) when the mean neutral hydrogen fraction (x_HI) and statistical properties of the universe change rapidly. The 3D power spectrum only quantifies the ergodic part of the signal and fails to capture the variation of the x_HI. The multi-frequency angular power spectrum (MAPS), on the other hand, quantifies the entire second-order statistics of the signal in the presence of the LC effect, including the homogeneous and isotropic statistical fluctuations along all three spatial directions and systematic variation along the LoS direction due to cosmological evolution. We propose a new method to observationally determine the reionization history along with the power spectrum by assuming a model where the systematic frequency dependence of MAPS arises entirely due to the evolution of the mean neutral hydrogen fraction, whereas the ergodic part of the MAPS carries the information of the homogeneous and isotropic statistical fluctuations. We validate our method by calculating MAPS from simulated LC EoR 21-cm datasets for different statistically independent realizations and using the Markov Chain Monte Carlo (MCMC) method. We demonstrate that it is possible to determine the reionization history across the entire observational bandwidth and the power spectrum monopole and quadrupole moments simultaneously using the complete information in the observed MAPS.
