J/ApJS/275/46 Unobscured QSO cand. in the southern sky with KS4 (Kim+, 2024)
Exploring unobscured quasi-stellar objects in the Southern Hemisphere with KS4.
Kim Y., Kim M., Im M., Chang S.-W., Jeong M., Byun W., Kim J., Kim D.,
Shim H., Song H.
<Astrophys. J. Suppl. Ser., 275, 46 (2024)>
=2024ApJS..275...46K 2024ApJS..275...46K
ADC_Keywords: QSOs; Photometry, UBVRI; Photometry, infrared; Surveys
Keywords: Quasars ; Photometry ; Catalogs ; Galaxies
Abstract:
We present a catalog of unobscured quasi-stellar object (QSO)
candidates in the Southern Hemisphere from the early interim data of
the KMTNet Synoptic Survey of Southern Sky (KS4). The KS4 data covers
∼2500deg2 sky area, reaching 5σ detection limits of
∼22.1-22.7 AB mag in the BVRI 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 distribution fitting results. The final catalog
contains 72964 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 z<2 within the KS4 survey area. In addition,
the number count of our candidates is comparable to that of
spectroscopically confirmed QSOs from the Sloan Digital Sky Survey in
the northern sky. These demonstrate that our approach is effective in
searching for unobscured QSOs in the southern sky. Future
spectrophotometric surveys covering the southern sky will enable us to
discern their true nature and enhance our understanding of QSO
populations in the Southern Hemisphere.
Description:
The data used in this work consists of object catalogs from BVRI
stacked images for 638 KMTNet Synoptic Survey of Southern Sky (KS4)
tiles (∼2500deg2). Each predefined tile covers a total field of
2°x2°, matching the field of view of the KMTNet camera.
Observations were made using three identical 1.6m telescopes between
late 2019 November and 2022 January. We prioritized observations in
areas of the sky excluding the Large Magellanic Cloud, Small
Magellanic Cloud, low-Galactic-latitude regions (|b|<9°), and the
regions already covered by the DES (Dark Energy Survey).
Each tile is observed with a 120s exposure per visit, with a total
combined exposure time of at least 480s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 217 72964 KMTNet Synoptic Survey of Southern Sky (KS4)
QSO candidate catalog
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/367 : The VISTA Hemisphere Survey (VHS) catalog DR5 (McMahon+, 2020)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
VII/223 : The 2dF QSO Redshift Survey. V. The 10k catalogue (Croom+ 2001)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
VII/294 : The Million Quasars (Milliquas) catalogue, version 8 (Flesch, 2023)
J/PASP/110/863 : A Stellar Spectral Flux Library: 1150 - 25000 A (Pickles 1998)
J/AJ/123/567 : SDSS quasar catalog, I: Early Data Release (Schneider+, 2002)
J/ApJ/613/682 : AGN central masses & broad-line region sizes (Peterson+, 2004)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
J/ApJ/663/81 : SED of hard X-ray selected AGN in XMDS (Polletta+, 2007)
J/AJ/136/2373 : Type 2 quasars from SDSS (Reyes+, 2008)
J/ApJ/679/140 : IR measurement of quasar obscuration (Treister+, 2008)
J/ApJ/690/1236 : COSMOS photometric redshift catalog (Ilbert+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/764/45 : Luminosity function of broad-line quasars. II. (Kelly+, 2013)
J/ApJ/778/98 : Cross-correlation of SDSS QSOs and BOSS galaxies (Shen+, 2013)
J/ApJ/806/109 : Rest-frame optical spectra of 3<z<6 QSOs (Jun+, 2015)
J/ApJ/821/56 : Space telescope RM project. III. NGC 5548 (Fausnaugh+, 2016)
J/ApJ/841/76 : Intrinsic far-IR SED of luminous AGNs (Lyu+, 2017)
J/ApJS/234/23 : The WISE AGN candidates catalogs (Assef+, 2018)
J/ApJ/886/33 : MIR reverberation mapping of z<0.5 PG AGNs (Lyu+, 2019)
J/ApJ/896/1 : SEAMBHs. XI. Mrk 142 X-ray--opt. light curves (Cackett+, 2020)
J/ApJ/900/58 : Opt-IR LC compilation of DES Stripe 82 quasars (Yang+, 2020)
J/ApJ/916/47 : GECKO follow-up obs. of 3 binary BH GW events (Kim+, 2021)
J/ApJS/268/57 : Unobscured QSOs in ecliptic poles (Byun+, 2023)
J/ApJS/264/9 : Southern phot. QSOs from DES DR2 & NIR surveys (Yang+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [KS4Q]
6- 24 A19 --- KS4Q KS4 QSO candidate designation
(JHHMMSS.ss+DDMMSS.s)
26- 34 F9.5 deg RAdeg Right Ascension (J2000)
36- 44 F9.5 deg DEdeg [-85/-28.9] Declination (J2000)
46- 51 F6.3 mag Bmag [15/23.3] KS4 B-band MAG_AUTO
extinction-corrected AB magnitude
53- 57 F5.3 mag e_Bmag [0.007/0.5] Error on Bmag
59- 64 F6.3 mag Vmag [15/27]?=99 KS4 V-band MAG_AUTO
extinction-corrected AB magnitude
66- 71 F6.3 mag e_Vmag [0.01/28]?=99 Error on Vmag
73- 78 F6.3 mag Rmag [14.87/22.81] KS4 R-band MAG_AUTO
extinction-corrected AB magnitude
80- 84 F5.3 mag e_Rmag [0.009/0.7] Error on Rmag
86- 91 F6.3 mag Imag [14.77/22.21] KS4 I-band MAG_AUTO
extinction-corrected AB magnitude
93- 97 F5.3 mag e_Imag [0.009/0.2] Error on Imag
99- 105 F7.3 mag Jmag [14.6/24.1]?=-99 J-band extinction-corrected AB
magnitude
107- 113 F7.3 mag e_Jmag [0.002/10.8]?=-99 Error on Jmag
115- 119 F5.3 --- f_Jmag [0/2] Flag in J-band (1)
121- 127 F7.3 mag Hmag [13.67/20.55]?=-99 H-band extinction-corrected
AB magnitude
129- 135 F7.3 mag e_Hmag [0.005/0.4]?=-99 Error on Hmag
137- 141 F5.3 --- f_Hmag [0/2] Flag in H-band (1)
143- 149 F7.3 mag Ksmag [13/19.91]?=-99 K_s-band extinction-corrected AB
magnitude
151- 157 F7.3 mag e_Ksmag [0.002/0.5]?=-99 Error on Ksmag
159- 163 F5.3 --- f_Ksmag [0/2] Flag in K_s-band (1)
165- 170 F6.3 mag W1mag [13.28/21.3] WISE W1-band extinction-corrected
AB magnitude
172- 176 F5.3 mag e_W1mag [0.02/0.5] Error on W1mag
178- 183 F6.3 mag W2mag [12.86/20.5] WISE W2-band extinction-corrected
AB magnitude
185- 189 F5.3 mag e_W2mag [0.019/0.4] Error on W2mag
191- 196 F6.3 mag W3mag [11.89/18.87] WISE W3-band extinction-corrected
AB magnitude
198- 202 F5.3 mag e_W3mag [0.015/0.5] Error on W3mag
204- 209 F6.3 mag W4mag [10.83/16.86] WISE W4-band extinction-corrected
AB magnitude
211- 217 F7.3 mag e_W4mag [0.02/0.6]?=-99 Error on W4mag
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Note (1): Flags on JHKs magnitudes as follows:
0.0 = no data;
1.0 = VISTA Hemisphere Survey (VHS, see II/367) data;
2.0 = Two Micron All Sky Survey (2MASS, see II/246) data.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Oct-2025