Neutral hydrogen (HI) is the most abundant element in our Universe, and observations of its 21-cm (1420.4 MHz) radiation are essential to understand galactic structure, the distribution of dark matter in galaxies, and galactic environmental interactions. The sensitivity of current instruments has limited HI survey depths to up to z~0.5. However, the Looking At the Distant Universe with the MeerKAT Array (LADUMA) survey will be able to detect HI emission out to z~1.4, and surveys by the Square Kilometer Array Observatory (SKAO) will be able to push HI surveys even further.
We developed a library for Lightweight HI source finding for next generation radio surveys (LiSA). LiSA was developed and tested on the Square Kilometer Array Science Data Challenge 2 (SDC2) dataset, and contains algorithms for 2D-1D wavelet denoising using the starlet transform and flexible source finding using null-hypothesis testing. These algorithms are lightweight and portable, needing only a few user-defined parameters reflecting the resolution of the data. A data anlysis pipeline developed using LiSA was able to find 95% of HI sources with SNR > 3 and accurately predict their properties, taking 6th place out of 40 teams in SDC2.
