Deep radio-interferometric imaging with POLISH: DSA-2000 and weak lensing

Abstract

ABSTRACT Radio interferometry allows astronomers to probe small spatial scales that are often inaccessible with single-dish instruments. However, recovering the radio sky from an interferometer is an ill-posed deconvolution problem that astronomers have worked on for half a century. More challenging still is achieving resolution below the array’s diffraction limit, known as superresolution imaging. To this end, we have developed a new learning-based approach for radio interferometric imaging, leveraging recent advances in the classical computer vision problems of single-image superresolution and deconvolution. We have developed and trained a high-dynamic range residual neural network to learn the mapping between the dirty image and the true radio sky. We call this procedure POLISH, in contrast to the traditional CLEAN algorithm. The feed-forward nature of learning-based approaches like POLISH is critical for analysing data from the upcoming Deep Synoptic Array (DSA-2000). We show that POLISH achieves superresolution, and we demonstrate its ability to deconvolve real observations from the Very Large Array. Superresolution on DSA-2000 will allow us to measure the shapes and orientations of several hundred million star-forming radio galaxies (SFGs), making it a powerful cosmological weak lensing survey and probe of dark energy. We forecast its ability to constrain the lensing power spectrum, finding that it will be complementary to next-generation optical surveys such as Euclid.