KMTNet Synoptic Survey of Southern Sky III: The First Data Release

TL;DR

The paper announces the first data release of the KMTNet Synoptic Survey of the Southern Sky, providing deep, wide-field imaging data and catalogs for astrophysical research, with validated high data quality and public accessibility.

Contribution

This is the first public data release of the KMTNet survey, offering extensive imaging data and source catalogs for the southern sky with validated quality and uniform coverage.

Findings

Deep co-added images reach 22.0-23.5 AB mag depth.

Over 200 million sources cataloged with SNR > 5.

Astrometric accuracy within 0.13 arcsec relative to Gaia.

Abstract

We present the first public data release (DR1) of the KMTNet Synoptic Survey of Southern Sky (KS4). This deep, wide-field imaging survey covers a southern footprint of -85$^{\circ}$ < Decl. < -28.8$^{\circ}$ in the $B$, $V$, $R$, and $I$ bands using a network of three 1.6-m telescopes. Although primarily designed to secure reference imaging for gravitational wave counterpart identification, DR1 delivers science-ready data for $\sim$4,000 deg$^{2}$ to enable a broad range of astrophysical research. The release includes deep co-added images reaching median 5$\sigma$ depths of 22.0-23.5 AB mag. It is accompanied by two source catalogs containing over 200 million sources with SNR $>5$: an $I$-band-selected forced-photometry catalog optimized for consistent colors, and a band-merged catalog offering enhanced completeness. Validation demonstrates robust data quality, characterized by mean astrometric offsets of $+0.054 \pm 0.129$ arcsec in RA and $-0.015 \pm 0.120$ arcsec in Dec relative to Gaia DR3. {\refbf Photometric uniformity for point sources is maintained within $\pm 0.03$ mag relative to Gaia XP for 97.5--99.8\% of the footprint across all four bands.} A key advantage of KS4 is its uniform and contiguous spatial coverage. It extends to fainter magnitudes than other uniform surveys while filling irregular gaps in existing deep datasets. All data products are publicly available via the CDS and NOIRLab's Astro Data Lab.