Visibility stacking with MeerKAT : opportunities and pitfalls

Abstract

Stacking is a statistical approach to measure the average properties for known objects that are too faint to be detected individually at the target wavelength. This approach has been extensively used for studies of high redshift, and/or intrinsically faint galaxies with a wide range of telescopes, including radio inteferometers. The technique is typically applied using images rather than the direct measurement of an interferometer, namely Fourier components of the sky brightness distribution. However, interferometry is not a direct imaging method, and this imposes several challenges to stacking, limiting scientific inference. This thesis tests where visibility stacking might be more effective than the traditional image-plane stacking approach using simulated data, as well as real observations from the MeerKAT telescope. To do so, we perform a suite of visibility stacking experiments on realistic synthetic data generated from the TRECS Square Kilometre Array simulations. Parameters that are varied include the CLEAN depth, stacking depth and the maximum source distance from the phase centre. We further investigate the applications of visibility stacking on real MeerKAT data. The stacking techniques are applied on HI-selected galaxies within the Abell 3408 galaxy cluster. Our simulated and real data results suggest that visibility stacking produces favourable results compared to image-stacking for shallow observations, but caution must be applied to sub-µJy stacked sensitivity experiments.