Speaker
Description
Using the SKAO to map the intensity of neutral hydrogen’s 21cm emission line will be a golden opportunity to constrain models of cosmology. Neutral hydrogen will reside around peaks in the late Universe's underlying density field, the clustering of which is rich in cosmological information. I will present results from MeerKAT pilot surveys where the 64 single-dishes scan the sky in auto-correlation mode, providing 21cm intensity maps that cover ~200 square degrees at redshift z~0.43. We find strong correlations between the MeerKAT pilot survey intensity maps and overlapping galaxy catalogues from optical telescope surveys. This is strong evidence for detecting large-scale cosmic structure within the 21cm intensity maps since the galaxies are a known tracer of the underlying dark matter density field. The cross-correlations between 21cm intensity maps and optical galaxies are a powerful technique for understanding and mitigating systematics, allowing for cosmological signatures to be revealed, which are otherwise dominated by contaminants in the low signal-to-noise pilot survey data. This is the first time such detection has been made with an array of dishes operating in single-dish mode, validating the technique that will be used with the arriving SKAO. The SKA-Mid will also present an upgrade in sensitivity relative to MeerKAT. Furthermore, the Band 1 receivers will provide a deeper redshift range, meaning the volumes we can span in these maps will increase by several orders of magnitude. This will allow more precise constraints and larger scales to be probed, making the SKAO a powerful instrument for cosmology.
