arXiv subjects

Sungho Jung

Publications and source records attributed to Sungho Jung.

3 recordsLinked to original sources

arXiv2026

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

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$σ$ 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.

astro-ph.IM↗

arXiv2026

KMTNet Synoptic Survey of Southern Sky II: Data Reduction and Real-Time Transient Detection Pipeline

We present a comprehensive pipeline developed for the image processing of the KMTNet Synoptic Survey of the Southern Sky (KS4) Data Release 1. This pipeline encompasses several key processes, including data quality assurance, astrometry, photometric zero-point (ZP) calibration, bad pixel masking, image stacking, and difference image analysis (DIA). The astrometric solutions were validated by cross-matching with the Gaia EDR3 catalog, achieving sub-pixel astrometric accuracy (< 0.4 arcsec). To ensure spatial consistency, we divided each image into multiple subsections and confirmed that astrometric accuracy was maintained even at the edges. We performed a two-stage photometric calibration. Initial ZP solutions were computed for each individual image frame using the APASS DR9 and SkyMapper DR3 catalogs. Subsequently, we corrected residual spatial variations in the stacked images using Gaia XP photometry. This procedure yielded a 5-sigma depth of 22-23 AB mag across the BVRI bands, with root-mean-square errors of approximately 0.03 mag when referenced to Gaia stars in the magnitude range of 14-19 mag. The processed KS4 images span over 4,000 deg^2 of the southern sky, providing reference images suitable for DIA. This publicly available pipeline also supports real-time processing of newly acquired images, enabling prompt transient detection. We demonstrate its effectiveness through successful applications in gravitational-wave follow-up observations.

astro-ph.IM↗

arXiv2025

AllBRICQS: The Discovery of Luminous Quasars in the Northern Hemisphere

We present the second catalog of bright quasars from the All-sky BRIght, Complete Quasar Survey (AllBRICQS), focusing on spectroscopically observed quasars in the Northern Hemisphere with Galactic latitude $|b| > 10^\circ$. This catalog includes their spectral data, redshifts, and luminosities. AllBRICQS aims to identify the last remaining optically bright quasars using data from the Wide-field Infrared Survey Explorer (WISE) and Gaia all-sky survey Data Release 3 (DR3). AllBRICQS searches for quasars that are brighter than $B_P = 16.5$ or $R_P = 16$ mag in Gaia DR3, based on simple selection criteria. Here, we report 62 new AllBRICQS quasars spanning various types, which include typical broad emission line quasars and the most luminous iron low-ionization broad absorption line quasars discovered to date. Spectroscopic observations were conducted using the Long-Slit Spectrograph on the 1.8-meter telescope at Bohyunsan Optical Astronomy Observatory, YFOSC on the 2.4-meter telescope at Lijiang Observatory, and BFOSC on the 2.16-meter telescope at Xinglong Observatory. We applied flux calibration using ZTF broadband photometry to correct for attenuation due to intermittent thin clouds during the observations. Redshifts were determined using inverse-variance weighted cross-correlation methods. Our targets span the bolometric luminosity range of $44.9<\log \left( L_{\rm bol} / {\rm erg~s^{-1}} \right)<48.0$ at redshifts between 0.09 and 2.48. These confirmed AllBRICQS quasars provide a valuable resource for future research into quasar evolution, black holes, their environments, and their host galaxies across multiple wavelengths.

astro-ph.GA↗