J/ApJS/280/68 SHELLQs. XXIV. Obscured quasar candidates (Matsuoka+, 2025)
Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs).
XXIV. 54 new quasars and candidate obscured quasars at 5.71≤z≤7.02.
Matsuoka Y., Iwasawa K., Onoue M., Izumi T., Strauss M.A., Akiyama M.,
Aoki K., Arita J., Ding X., Imanishi M., Kashikawa N., Kawaguchi T.,
Kikuta S., Kohno K., Lee C.-H., Nagao T., Phillips C.L., Sawamura M.,
Silverman J.D., Takahashi A., Toba Y.
<Astrophys. J. Suppl. Ser., 280, 68 (2025)>
=2025ApJS..280...68M 2025ApJS..280...68M
ADC_Keywords: QSOs; Spectra, red; Redshifts; Magnitudes, absolute;
Equivalent widths; Photometry, ugriz; Stars, brown dwarf
Keywords: Quasars ; High-redshift galaxies ; Reionization ; Sky surveys
Abstract:
We present spectroscopic identification of 43 quasars and 11 candidate
obscured quasars in the epoch of reionization (EoR) at 5.71≤z≤7.02,
along with 29 galaxies at similar redshifts. This is the 24th
publication from the Subaru High-z Exploration of Low-Luminosity
Quasars (SHELLQs) project, which exploits the Hyper Suprime-Cam (HSC)
Subaru Strategic Program (SSP) imaging survey to search for EoR
quasars. The HSC-SSP survey has finished, and this paper is likely the
final installment of major (unobscured) quasar discoveries from the
SHELLQs project. In addition to the EoR objects, we identified five
strong [OIII] line emitters at z<1, 30 Galactic brown dwarfs, and
14 passive galaxies at z∼2, which contaminated our sample of
photometric quasar candidates. The present paper focuses on describing
the immediate outcome of the spectroscopic observations, while a
statistical analysis of the full SHELLQs sample will be presented in
our next publication.
Description:
The candidates presented here were selected from the S21A and S23B
internal data releases (DRs) of the Hyper Suprime-Cam (HSC) Subaru
Strategic Program (SSP) and are distributed across the entire 1100deg2
area of the completed HSC-SSP footprint.
Table 2 in the Appendix presents the journal of spectroscopic
observations for a total of 132 candidates. At the Subaru Telescope,
we used the Faint Object Camera and Spectrograph (FOCAS) to cover the
red-optical wavelengths from 0.75 to 1.0um with a spectral resolution
of R∼1200. All the observations have been carried out in the classical
mode, with the program IDs of S18B-011I, S22A-025, S22B-042, S24A-053,
and S24B-025.
At the Gran Telescopio Canarias (GTC), all the observations have been
conducted in the queue mode. The program IDs are GTC42-21B, GTC30-22A,
GTC23-24A, and GTC3-24B. We used the Optical System for Imaging and
low-intermediate-Resolution Integrated Spectroscopy (OSIRIS). The
R2500I grism was used, giving a spectral coverage from 0.75 to 1.0um
at a resolution of R∼1500.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 105 104 Spectroscopic properties
table2.dat 93 132 Journal of discovery spectroscopy
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See also:
II/382 : VIKING catalogue data release 4 (Cross+, 2012)
VII/292 : DESI Legacy Imaging Surveys DR8 photometric redshifts (Duncan, 2022)
J/MNRAS/477/2817 : Luminous Lyα emitters at z∼2-3 (Sobral+, 2018)
J/A+A/643/A149 : J-PLUS Lyα-emitting candidates (Spinoso+, 2020)
J/ApJS/259/18 : SHELLQs. XVI. New quasars at 5.8<z<7 (Matsuoka+, 2022)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Class Object class (1)
8- 26 A19 --- Name Name of the source (JHHMMSS.ss+DDMMSS.s)
28- 32 F5.3 --- z [0.78/7.02] Redshift (2)
34- 39 F6.2 mag M1450 [-26.1/-20.2]? Absolute 1450Å AB magnitude
41- 44 F4.2 mag e_M1450 [0.01/1.6]? M1450 uncertainty
46- 63 A18 --- Line Line identifier
65 A1 --- l_EWr Limit flag on EWr (3σ)
67- 72 F6.1 0.1nm EWr [0.4/5900]? Rest-frame equivalent width
74- 79 F6.1 0.1nm e_EWr [0.3/2900]? EWr uncertainty
81 A1 --- l_FWHM Limit flag on FWHM (3σ)
83- 87 I5 km/s FWHM [190/11000]? Line Full Width at Half Maximum
89- 92 I4 km/s e_FWHM [10/4000]? FWHM uncertainty
94- 99 F6.3 [10-7W] logL [40.9/44.7]? Log of the line luminosity in
erg/s
101- 105 F5.3 [10-7W] e_logL [0.01/0.4]? logL uncertainty
--------------------------------------------------------------------------------
Note (1): Class as follows:
qso = quasars (44 occurrences)
oqso = candidate obscured quasars (11 occurrences)
gal = galaxies (29 occurrences)
OIIIem = [OIII] emitters (20 occurrences for 5 sources)
Note (2): The redshifts of quasars, candidate obscured quasars, and galaxies
have uncertainties Δz∼0.01-0.1, depending on the spectral
features around Lyα (e.g., Matsuoka+ 2022, J/ApJS/259/18).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Class Object class (1)
8- 26 A19 --- Name Name of the source (JHHMMSS.ss+DDMMSS.s)
28 A1 --- l_imag Limit flag on imag (5σ significance)
30- 34 F5.2 mag imag [23.58/27.52] i-band AB magnitude (2)
36- 39 F4.2 mag e_imag [0.02/0.92]? Uncertainty on the imag
41 A1 --- l_zmag Limit flag on zmag (5σ significance)
43- 47 F5.2 mag zmag [21.59/26.4] z-band AB magnitude (2)
49- 52 F4.2 mag e_zmag [0.01/0.8]? Uncertainty on the zmag
54- 58 F5.2 mag ymag [20.66/26.5] y-band band AB magnitude (2)
60- 63 F4.2 mag e_ymag [0.01/1] Uncertainty on the ymag
65- 67 I3 min Texp [10/120] Exposure time
69- 79 A11 "Y/M/D" Date1 Date of observation (UT)
81- 91 A11 "Y/M/D" Date2 Date of observation (UT)
93 A1 --- Inst Instrument (3)
--------------------------------------------------------------------------------
Note (1): Class as follows:
bd = brown dwarfs (30 occurrences)
pgal = passive galaxies (14 occurrences)
qso = quasars (43 occurrences)
oqso = candidate obscured quasars (11 occurrences)
gal = galaxies (29 occurrences)
OIIIem = [OIII] emitters (5 occurrences)
Note (2): All magnitudes were taken from the Hyper Suprime-Cam (HSC)
Subaru Strategic Program (SSP) S23B data release, and
were corrected for Galactic extinction.
Note (3): Instrument as follows:
F = Subaru/FOCAS (94 occurrences)
O = GTC/OSIRIS (38 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
License: CC-BY-4.0
References:
Matsuoka et al. Paper I. 2016ApJ...828...26M 2016ApJ...828...26M
Matsuoka et al. Paper II. 2018PASJ...70S..35M 2018PASJ...70S..35M
Izumi et al. Paper III. 2018PASJ...70...36I 2018PASJ...70...36I
Matsuoka et al. Paper IV. 2018ApJS..237....5M 2018ApJS..237....5M
Matsuoka et al. Paper V. 2018ApJ...869..150M 2018ApJ...869..150M
Onoue et al. Paper VI. 2019ApJ...880...77O 2019ApJ...880...77O
Izumi et al. Paper VIII. 2019PASJ...71..111I 2019PASJ...71..111I
Kato et al. Paper IX. 2020PASJ...72...84K 2020PASJ...72...84K
Matsuoka et al. Paper X. 2019ApJ...883..183M 2019ApJ...883..183M
Ishimoto et al. Paper XI. 2020ApJ...903...60I 2020ApJ...903...60I
Izumi et al. Paper XII. 2021ApJ...908..235I 2021ApJ...908..235I
Izumi et al. Paper XIII. 2021ApJ...914...36I 2021ApJ...914...36I
Onoue et al. Paper XIV. 2021ApJ...919...61O 2021ApJ...919...61O
Lu et al. Paper XV. 2022MNRAS.517.1264L 2022MNRAS.517.1264L
Matsuoka et al. Paper XVI. 2022ApJS..259...18M 2022ApJS..259...18M Cat. J/ApJS/259/18
Takahashi et al. Paper XVII. 2024ApJ...960..112T 2024ApJ...960..112T
Arita et al. Paper XVIII. 2023ApJ...954..210A 2023ApJ...954..210A
Iwamoto et al. Paper XXI. 2025ApJ...979..183I 2025ApJ...979..183I
Iwasawa et al. Paper XXII. 2026A&A...706A.305I 2026A&A...706A.305I
Hoshi et al. Paper XXIII. 2025MNRAS.539.2039H 2025MNRAS.539.2039H
Matsuoka et al. Paper XXIV. 2025ApJS..280...68M 2025ApJS..280...68M This catalog
Arita et al. Paper XXV. 2026MNRAS.549g.784A 2026MNRAS.549g.784A
(End) Emmanuelle Perret [CDS] 15-Jun-2026