A new window onto the LSB near-infrared universe

LSST:UK team members have collaborated on a new paper in the journal Astronomy & Astrophysics: NASIM: Revealing the low surface brightness Universe from legacy VISTA data.

Ground-based exploration of the low-surface-brightness (LSB) Universe in the near-infrared has long been hindered by the intense atmospheric background, which overwhelms faint extended structures. Yet these wavelengths are vital for tracing old stellar populations that dominate galaxy outskirts, offering unique clues to their assembly and evolution. To tackle this challenge, Elham Saremi and collaborators have developed NASIM (Near-infrared Automated low Surface brightness reduction In Maneage)—a fully automated and reproducible reduction pipeline optimised for VISTA/VIRCAM data. 

NASIM incorporates advanced methods from the GNU Astronomy Utilities (Gnuastro) to eliminate large-scale artefacts and detector patterns while safeguarding diffuse emission essential for LSB science. Key innovations include an adaptive flat-fielding technique, a conservative sky subtraction strategy tailored to extended light, and weighted stacking with robust outlier rejection, producing clean reductions that retain even the faintest structures. 

Although applicable to all VISTA/VIRCAM surveys, this paper demonstrates the pipeline’s capabilities on the Ks-band dataset of the Euclid Deep Field South (KEDFS), also serving as LSST’s fifth deep drilling field. With NASIM, the reduction achieves a surface brightness depth of ~27.7 mag arcsec-2 (3σ over 100 arcsec²); about 67 times deeper than 2MASS and 11 times deeper than the VISTA Hemisphere Survey. Looking ahead, NASIM is poised to become a cornerstone for near-infrared LSB studies, complementing missions such as Euclid, Roman, and ARRAKIHS, and enhancing LSST–VISTA data fusion pipelines. Its open and reproducible design sets a benchmark for reliable science in the era of large surveys. 

Download the paper

NASIM: Revealing the low surface brightness Universe from legacy VISTA data