Deep Radio Interferometric Imaging with POLISH: DSA-2000 and weak lensing

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 super-resolution imaging. To this end, we have developed a new learning-based approach for radio interferometric imaging, leveraging recent advances in the computer vision problems deconvolution and single-image super-resolution (SISR). 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 analyzing data from the upcoming Deep Synoptic Array (DSA-2000). We show that POLISH achieves super-resolution, and we demonstrate its ability to deconvolve real observations from the Very Large Array (VLA). Super-resolution 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.

Image reconstruction algorithms in radio interferometry: from handcrafted to learned regularization denoisers

“…The reconstructions are however affected by patching artefacts. Most recently, Connor et al (2021) developed a DNN dubbed POLISH, show promising results on simulations for a simple super-resolution task, also demonstrating an ability to perform endto-end reconstruction on point-like sources from Very Large Array (VLA) observations. In summary, beyond the generalizability and interpretability issues, these approaches have neither been thoroughly validated for high resolution high dynamic range imaging of complex structure involving diffuse and faint emission, nor compared with both CLEAN and state-of-the-art optimization approaches.…”