HI intensity mapping with MeerKAT: A measurement of the 21-cm auto-spectrum on cosmological scales
Researchers directly measured the 21-cm signal from neutral hydrogen (HI) at redshift $z=0.42$ using intensity mapping data from MeerKAT. By splitting data into subsets and using internal cross-correlations, they successfully isolated the cosmological HI auto-spectrum on large scales ($k < 0.245 h ext{ Mpc}^{-1}$). This provided a robust constraint on the clustering amplitude of HI, marking a milestone for future SKA surveys.