The MeerKLASS L-band On-the-Fly Continuum Survey: Data Release 1

Abstract: The MeerKAT Large Area Synoptic Survey (MeerKLASS) collaboration has acquired multiple passes of L-band (856-1712 MHz) scanning observations over a 268 deg$^2$ sky region. This scanning enables efficient, large-area sky surveys by continuously scanning the MeerKAT array back and forth at fixed elevation while recording data at 2 sec intervals, progressively covering the survey region as the Earth rotates. We employ a novel on-the-fly (OTF) interferometric imaging technique to construct continuum images and catalogs from 16 hours of scan data. These data products, constituting the first MeerKLASS L-band data release (DR1), consist of high-fidelity radio continuum images and a catalogue of 34,874 radio sources detected with a SNR$>$9. The resulting Stokes I images achieve a median noise level of 33 $μ$Jy\,beam$^{-1}$ and a median angular resolution of approximately $25.5''\times 7.8''$. Cross-comparisons with previous surveys confirm the consistency of our flux density scale within 5\% and astrometric precision within $1.5''$. Additionally, flux densities measured across the seven sub-bands enable in-band spectral-index estimates for the detected sources, providing insights into their physical properties and the broader source population. We compute the differential source counts, finding good agreement with existing measurements and validating our end-to-end processing. This data release demonstrates the effectiveness of scanning surveys when combined with OTF interferometric imaging. Commensal intensity mapping and interferometric imaging offers a dramatic enhancement of survey science per invested hour of observations and could therefore be an appealing option for next generation facilities like SKA-Mid.