Exploring Unobscured QSOs in the Southern Hemisphere with KS4
Yongjung Kim, Minjin Kim, Myungshin Im, Seo-Won Chang, Mankeun Jeong,, Woowon Byun, Joonho Kim, Dohyeong Kim, Hyunjin Shim, Hyunmi Song

TL;DR
This paper introduces a new catalog of nearly 73,000 unobscured QSOs in the southern hemisphere, identified through combined optical and infrared data, demonstrating high recovery rates and comparable counts to northern surveys.
Contribution
The study presents a novel selection method for unobscured QSOs using multi-wavelength data, resulting in a large, effective catalog for the southern sky.
Findings
Catalog contains 72,964 QSO candidates with high purity.
87% recovery rate for spectroscopically confirmed QSOs at z<2.
Number counts are comparable to northern sky surveys.
Abstract
We present a catalog of unobscured QSO candidates in the southern hemisphere from the early interim data of the KMTNet Synoptic Survey of Southern Sky (KS4). The KS4 data covers sky area, reaching 5 detection limits of 22.1-22.7 AB mag in the bands. Combining this with available infrared photometric data from the surveys covering the southern sky, we select the unobscured QSO candidates based on their colors and spectral energy distributions (SEDs) fitting results. The final catalog contains 72,964 unobscured QSO candidates, of which only 0.4% are previously identified as QSOs based on spectroscopic observations. Our selection method achieves an 87% recovery rate for spectroscopically confirmed bright QSOs at within the KS4 survey area. In addition, the number count of our candidates is comparable to that of spectroscopically…
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Taxonomy
TopicsAtmospheric and Environmental Gas Dynamics
