Radio galaxy detection in the visibility domain

We explore a new Bayesian method of detecting galaxies from radio interferometric data of the faint sky. Working in the Fourier domain, we fit a single, parameterized galaxy model to simulated visibility data of star-forming galaxies. The resulting multimodal posterior distribution is then sampled using amultimodal nested sampling algorithm such as MULTINEST. For each galaxy, we construct parameter estimates for the position, flux, scale length, and ellipticities from the posterior samples. We first test our approach on simulated SKA1-MID visibility data of up to 100 galaxies in the field of view (FOV), considering a typical weak lensing survey regime (SNR ≥ 10) where 98 per cent of the input galaxies are detected with no spurious source detections. We then explore the low-SNR regime, finding our approach reliable in galaxy detection and providing in particular high accuracy in positional estimates down to SNR ∼ 5. The presented method does not require transformation of visibilities to the image domain, and requires no prior knowledge of the number of galaxies in the FOV, thus could become a useful tool for constructing accurate radio galaxy catalogues in the future.