Speaker
Description
The redshifted 21-cm signal emitted by neutral Hydrogen (HI) is a promising probe to understand the evolution of the topology and morphology of ionised regions during the Epoch of Reionisation (EoR). The morphology of ionised regions allows us to infer the nature and properties of ionising sources, i.e., early galaxies and AGNs. Traditional Fourier statistics, such as the power spectrum, help us quantify the strength of fluctuations in this field at different length scales but do not preserve its phase information. Analysing the 21-cm brightness temperature field in the image domain retains its non-Gaussian characteristics and morphological information. The coalescence of multiple ionised regions to form one contiguous ionised region spanning the universe is known as percolation, and its onset is quantified by the value of the Largest Cluster Statistic (LCS) approaching 1. In this work, we perform a percolation analysis of interferometric 21-cm brightness temperature maps to be observed by SKA-Low by studying the redshift evolution of the LCS along a lightcone to distinguish between several simulated reionisation source models. We have extended previous results on reionisation model comparison from the analysis of coeval 21-cm maps to understand how the lightcone effect, which is inherent to observations where multiple spectral channels are used to understand the time evolution of the signal, biases the observed percolation behaviour and affects the distinguishability of the source models. We estimate the LCS of subvolumes of varying sizes in the 21-cm lightcone maps and study their redshift evolution across different reionisation scenarios using a moving-volume approach. We comment on the spectral bandwidth corresponding to the size of the optimal subvolume that allows the least biased recovery of the percolation transition under different reionisation scenarios.
