Deconvolution for Large Astronomical Surveys: A Study of the Scaled Gradient Projection Method on Zwicky Transient Facility Data

TL;DR

Addresses resolution loss in ground-based astronomical imaging and demonstrates a non-blind single-band deconvolution using Scaled Gradient Projection (SGP) on ZTF data. SGP minimizes the Poisson KL divergence with a diagonal scaling and projection step, improving convergence over Richardson-Lucy and enabling efficient processing of large images. Results show the deconvolved sources have FWHM ≈ 1 pixel ($FWHM ≈ 1$ pixel in the deconvolved frame), preserve flux for bright sources while reducing flux uncertainties for faint ones, and reach detection completeness around 99.6% relative to the observed detections; it also reveals new faint sources validated by crossmatches with DESI Legacy DR10 and Pan-STARRS1 and uncovers potential deblends with magnitude differences up to about 3 mag and separations near 1 arcsecond. The method yields speedups of roughly eightfold compared with Richardson-Lucy and is suitable for incorporation into survey pipelines to improve deblending and transient analyses.

Abstract

Ground-based astronomical observations will continue to produce resolution-limited images due to atmospheric seeing. Deconvolution reverses such effects and thus can benefit extracted science in multifaceted ways. We apply the Scaled Gradient Projection (SGP) algorithm for the single-band deconvolution of several observed images from the Zwicky Transient Facility and mainly discuss the performance on stellar sources. The method shows good photometric flux preservation, which deteriorates for fainter sources but significantly reduces flux uncertainties even for the faintest sources. Deconvolved sources have a well-defined Full-Width-at-Half-Maximum (FWHM) of roughly one pixel (one arcsecond for ZTF) regardless of the observed seeing. Detection after deconvolution results in catalogs with $\gtrsim$99.6% completeness relative to detections in the observed images. A few observed sources that could not be detected in the deconvolved image are found near saturated sources, whereas for others, the deconvolved counterparts are detected when slightly different detection parameters are used. The deconvolution reveals new faint sources previously undetectable, which are confirmed by crossmatching with the deeper DESI Legacy DR10 and with Pan-STARRS1 through forced photometry. The method could identify examples of serendipitous potential deblends that exceeded SExtractor's deblending capabilities, with as extreme as $Δm \approx 3$ and separations as small as one arcsecond between the deblended components. Our survey-agnostic approach is better and eight times faster than Richardson-Lucy deconvolution and could be a reliable method for incorporation into survey pipelines.