# Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs). XVI. 69 New
Quasars at $5.8<z<7.0$

Yoshiki Matsuoka  Research Center for Space and Cosmic Evolution, Ehime
University, Matsuyama, Ehime 790-8577, Japan.  Kazushi Iwasawa  ICREA and
Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Martí i
Franquès, 1, 08028 Barcelona, Spain.  Masafusa Onoue  Max-Planck-Institut für
Astronomie, Königstuhl 17, D-69117, Heidelberg, Germany.  Takuma Izumi
National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.
Nobunari Kashikawa  Department of Astronomy, School of Science, The University
of Tokyo, Tokyo 113-0033, Japan.  Michael A. Strauss  Department of
Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ
08544, USA.  Masatoshi Imanishi  National Astronomical Observatory of Japan,
Mitaka, Tokyo 181-8588, Japan.  Department of Astronomical Science, Graduate
University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan.
Tohru Nagao  Research Center for Space and Cosmic Evolution, Ehime University,
Matsuyama, Ehime 790-8577, Japan.  Masayuki Akiyama  Astronomical Institute,
Tohoku University, Aoba, Sendai, 980-8578, Japan.  John D. Silverman  Kavli
Institute for the Physics and Mathematics of the Universe, WPI, The University
of Tokyo, Kashiwa, Chiba 277-8583, Japan.  Naoko Asami  Seisa University,
Hakone-machi, Kanagawa, 250-0631, Japan.  James Bosch  Department of
Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ
08544, USA.  Hisanori Furusawa  National Astronomical Observatory of Japan,
Mitaka, Tokyo 181-8588, Japan.  Tomotsugu Goto  Institute of Astronomy and
Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
James E. Gunn  Department of Astrophysical Sciences, Princeton University,
Peyton Hall, Princeton, NJ 08544, USA.  Yuichi Harikane  Institute for Cosmic
Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582, Japan.
Hiroyuki Ikeda  National Institute of Technology, Wakayama College, Gobo,
Wakayama 644-0023, Japan.  Rikako Ishimoto  Department of Astronomy, School of
Science, The University of Tokyo, Tokyo 113-0033, Japan.  Toshihiro Kawaguchi
Department of Economics, Management and Information Science, Onomichi City
University, Onomichi, Hiroshima 722-8506, Japan.  Nanako Kato  Graduate School
of Science and Engineering, Ehime University, Matsuyama, Ehime 790-8577,
Japan.  Satoshi Kikuta  Center for Computational Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305-8577, Japan.  Kotaro Kohno  Institute of
Astronomy, The University of Tokyo, Mitaka, Tokyo 181-0015, Japan.  Research
Center for the Early Universe, University of Tokyo, Tokyo 113-0033, Japan.
Yutaka Komiyama  National Astronomical Observatory of Japan, Mitaka, Tokyo
181-8588, Japan.  Department of Astronomical Science, Graduate University for
Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan.  Chien-Hsiu Lee
NSF’s National Optical-Infrared Astronomy Research Laboratory, 950 North
Cherry Avenue, Tucson, AZ 85719, USA.  Robert H. Lupton  Department of
Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ
08544, USA.  Takeo Minezaki  Institute of Astronomy, The University of Tokyo,
Mitaka, Tokyo 181-0015, Japan.  Satoshi Miyazaki  National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.  Department of
Astronomical Science, Graduate University for Advanced Studies (SOKENDAI),
Mitaka, Tokyo 181-8588, Japan.  Hitoshi Murayama  Kavli Institute for the
Physics and Mathematics of the Universe, WPI, The University of Tokyo,
Kashiwa, Chiba 277-8583, Japan.  Atsushi J. Nishizawa  Institute for Advanced
Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Masamune Oguri  Department of Physics, Graduate School of Science, The
University of Tokyo, Bunkyo, Tokyo 113-0033, Japan  Kavli Institute for the
Physics and Mathematics of the Universe, WPI, The University of Tokyo,
Kashiwa, Chiba 277-8583, Japan.  Research Center for the Early Universe,
University of Tokyo, Tokyo 113-0033, Japan.  Yoshiaki Ono  Institute for
Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582, Japan
Masami Ouchi  Institute for Cosmic Ray Research, The University of Tokyo,
Kashiwa, Chiba 277-8582, Japan  Kavli Institute for the Physics and
Mathematics of the Universe, WPI, The University of Tokyo, Kashiwa, Chiba
277-8583, Japan.  Paul A. Price  Department of Astrophysical Sciences,
Princeton University, Peyton Hall, Princeton, NJ 08544, USA.  Hiroaki
Sameshima  Institute of Astronomy, The University of Tokyo, Mitaka, Tokyo
181-0015, Japan.  Naoshi Sugiyama  Kavli Institute for the Physics and
Mathematics of the Universe, WPI, The University of Tokyo, Kashiwa, Chiba
277-8583, Japan.  Graduate School of Science, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya 464-8602, Japan.  Philip J. Tait  Subaru Telescope, Hilo,
HI 96720, USA.  Masahiro Takada  Kavli Institute for the Physics and
Mathematics of the Universe, WPI, The University of Tokyo, Kashiwa, Chiba
277-8583, Japan.  Ayumi Takahashi  Graduate School of Science and Engineering,
Ehime University, Matsuyama, Ehime 790-8577, Japan.  Tadafumi Takata  National
Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.  Department
of Astronomical Science, Graduate University for Advanced Studies (SOKENDAI),
Mitaka, Tokyo 181-8588, Japan.  Masayuki Tanaka  National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.  Department of
Astronomical Science, Graduate University for Advanced Studies (SOKENDAI),
Mitaka, Tokyo 181-8588, Japan.  Yoshiki Toba  Department of Astronomy, Kyoto
University, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan.  Yousuke Utsumi  Kavli
Institute for Particle Astrophysics and Cosmology, Stanford University, CA
94025, USA.  Shiang-Yu Wang  Institute of Astronomy and Astrophysics, Academia
Sinica, Taipei, 10617, Taiwan.  Takuji Yamashita  National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.

(Received 2021 October 18; Revised 2021 November 19; Accepted 2021 November
23)

###### Abstract

We present the spectroscopic discovery of 69 quasars at $5.8<z<7.0$, drawn
from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) imaging survey
data. This is the 16th publication from the Subaru High-$z$ Exploration of
Low-Luminosity Quasars (SHELLQs) project, and completes identification of all
but the faintest candidates (i.e., $i$-band dropouts with $z_{\rm AB}<24$ and
$y$-band detections, and $z$-band dropouts with $y_{\rm AB}<24$) with Bayesian
quasar probability $P_{\rm Q}^{\rm B}>0.1$ in the HSC-SSP third public data
release (PDR3). The sample reported here also includes three quasars with
$P_{\rm Q}^{\rm B}<0.1$ at $z\sim 6.6$, which we selected in an effort to
completely cover the reddest point sources with simple color cuts. The number
of high-$z$ quasars discovered in SHELLQs has now grown to 162, including 23
type-II quasar candidates. This paper also presents identification of seven
galaxies at $5.6<z<6.7$, an [O III] emitter at $z=0.954$, and 31 Galactic cool
stars and brown dwarfs. High-$z$ quasars and galaxies comprise 75 % and 16 %
respectively of all the spectroscopic SHELLQs objects that pass our latest
selection algorithm with the PDR3 photometry. That is, a total of 91 % of the
objects lie at $z>5.6$. This demonstrates that the algorithm has very high
efficiency, even though we are probing an unprecedentedly low-luminosity
population down to $M_{1450}\sim-21$ mag.

high-redshift galaxies — quasars — reionization — supermassive black holes

##  1 Introduction

The astronomical community is making great strides toward charting and
understanding quasars at the epoch of cosmic reionization, which is thought to
have taken place during the interval $6<z<10$ (Planck Collaboration et al.,
2020). Quasars at $5.7<z\leq 7.0$ have been discovered from optical wide-field
($>$100-deg2 class) multi-band surveys, such as the Sloan Digital Sky Survey
(SDSS; Fan et al., 2000, 2001, 2003, 2004, 2006; Jiang et al., 2008, 2009,
2015), the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS; Willott et
al., 2005, 2007, 2009, 2010a, 2010b), the Panoramic Survey Telescope And Rapid
Response System 1 survey (Pan-STARRS1; Bañados et al., 2014, 2016; Venemans et
al., 2015; Mazzucchelli et al., 2017), the Dark Energy Survey (DES; Reed et
al., 2015, 2017, 2019; Yang et al., 2019), and the Dark Energy Spectroscopic
Instrument Legacy Imaging Surveys (DELS; Wang et al., 2017, 2018, 2019). Near-
infrared (IR) surveys are paving the way to probe more distant objects, and
indeed quasars at $z>6.5$ have been detected with, e.g., the United Kingdom
Infrared Telescope (UKIRT) Infrared Deep Sky Survey (Mortlock et al., 2011),
the Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-degree
Infrared Galaxy Survey (VIKING; Venemans et al., 2013), and the UKIRT and
VISTA Hemisphere Surveys, with three objects at $z=7.5-7.6$ marking the
highest-redshift quasars currently known (Bañados et al., 2018; Yang et al.,
2020; Wang et al., 2021). We will soon reach deeper into the epoch of
reionization with the advent of Euclid and the Roman Space Telescope. These
two space missions will provide unprecedentedly wide-and-deep maps of the
near-IR sky, and are expected to identify quasars up to $z\sim 10$ (e.g.,
Euclid Collaboration et al., 2019). High-$z$ quasars thus discovered have been
probing, and will further probe, the formation of the first supermassive black
holes (SMBHs) and their host galaxies, the history and sources of
reionization, and other key issues in the early universe.

We have been carrying out a high-$z$ quasar survey complementary to the
existing ones for the past several years, going much deeper in relatively
small areas of the sky. The project (“Subaru High-$z$ Exploration of Low-
Luminosity Quasars”; SHELLQs) exploits the exquisite imaging data produced by
the Hyper Suprime-Cam (HSC; Miyazaki et al., 2018) Subaru Strategic Program
(SSP) survey. Three layers named Wide, Deep, and UltraDeep constitute the HSC-
SSP survey, covering (1400, 26, 3.5) deg2 down to 5$\sigma$ limiting
magnitudes of $i_{\rm AB}$ = (25.9, 26.8, 27.4) for point sources,
respectively (Aihara et al., 2018). Thus far we have reported spectroscopic
identification of 93 low-luminosity quasars at $5.7<z<7.1$, including 18 type-
II quasar candidates with very luminous and narrow Ly$\alpha$ emission, in a
series of SHELLQs publications (Matsuoka et al., 2016, 2018a, 2018b, 2019a,
2019b). Follow-up near-IR spectroscopy has revealed that the quasars have a
variety of accretion modes, from sub-Eddington accretion onto massive SMBHs to
(super-)Eddington accretion onto less massive ones (Onoue et al., 2019, M.
Onoue et al., in prep.). The host galaxies probed with ALMA are also diverse,
sometimes accompanied by active star formation and powerful extended outflows
(Izumi et al., 2021a, b), while their dynamical masses are more or less
consistent with those inferred from the local mass relation between SMBHs and
the host bulges (Izumi et al., 2018, 2019).

This is the 16th publication from the SHELLQs project, presenting the
spectroscopic discovery of 69 new high-$z$ quasars accumulated over the past
two years. The basics of candidate selection and spectroscopic observations
are described in §2, followed by the results and discussion in §3. We use
point-spread-function (PSF) magnitudes ($m_{\rm AB}$) and associated errors
($\sigma_{\rm m})$ presented in the AB system (Oke & Gunn, 1983) unless
otherwise noted, corrected for Galactic extinction (Schlegel et al., 1998). We
refer to $z$-band magnitudes with the AB subscript (“$z_{\rm AB}$”), while
redshift $z$ appears without a subscript. The cosmological parameters are
assumed to be $H_{0}$ = 70 km s-1 Mpc-1, $\Omega_{\rm M}$ = 0.3, and
$\Omega_{\rm\Lambda}$ = 0.7.

##  2 Candidate selection and spectroscopy

Our candidate selection strategy remains mostly unchanged since the beginning
of the project, and is detailed in our previous papers. Here, we itemize the
essential steps, with an emphasis on recent updates.

  1. 1.

We first select point sources meeting the criteria
($z_{\rm AB}<24.5$ & $\sigma_{z}<0.155$ & $i_{\rm AB}-z_{\rm AB}>1.5$) OR
($y_{\rm AB}<25.0$ & $\sigma_{y}<0.217$ & $z_{\rm AB}-y_{\rm AB}>0.8$)
from the HSC-SSP database. The candidates selected with the first/second set
of conditions are referred to as $i$-/$z$-dropouts in what follows. Our
definition of “point sources” uses the ratio between the adaptive moment
(Hirata & Seljak, 2003) of a given source ($\mu$; averaged over the two image
dimensions) and that of the PSF model ($\mu_{\rm PSF}$). For $i$-dropouts, we
use the cut $0.7<\mu/\mu_{\rm PSF}<1.2$ measured in the $z$-band. This
criterion removes spectroscopic high-$z$ galaxies more efficiently than does
the condition we previously used (i.e., requiring that the difference between
the PSF and CModel magnitudes be less than 0.15), while retaining $>$90 % of
the high-$z$ broad-line quasars we identified (see Figure 8 of Matsuoka et
al., 2019a).111 The criterion is determined as a compromise between the
requirements to have high completeness and low contamination rates. A higher
value of the maximum allowed $\mu/\mu_{\rm PSF}$ selects quasars with larger
contribution of the host galaxies (e.g., Boutsia et al., 2021; Bowler et al.,
2021) as well as more galaxies without quasars (e.g., Ono et al., 2018).  A
looser cut, $0.6<\mu/\mu_{\rm PSF}<3.0$ measured in the $y$-band, is used for
$z$-dropouts, to be more inclusive. We exclude from the selection those
sources with $g$\- or $r$-band detections or any critical quality issues in
the photometry, such as those caused by saturation, cosmic rays, bad pixels,
and nearby bright stars. In addition, we eliminate the bluest candidates with
$i_{\rm AB}-z_{\rm AB}<2.5$ and $z_{\rm AB}-y_{\rm AB}<-1.0$, as we have found
that such sources are dominated by [O III] line emitters at $z\sim 0.8$ (see
below).

  2. 2.

The list of selected sources is matched to public near-IR survey catalogs. All
the objects presented in this paper were found from the HSC-SSP Wide layer,
where we use $Y$-, $J$-, $H$-, and $K$-band magnitudes measured with the UKIRT
Wide-Field Camera (WFCAM; Casali et al., 2007) or the VISTA Infrared Camera
(VIRCAM; Dalton et al., 2006). The data were obtained as a part of the UKIDSS
Large Area Survey (available in the data release [DR] 11PLUS), the UKIDSS
Hemisphere Survey (DR1), the VIKING (DR5), or the VISTA Hemisphere Survey
(DR6). The entire HSC-SSP Wide layer is covered in at least one band of the
above NIR surveys.

  3. 3.

We calculate a Bayesian probability ($P_{\rm Q}^{\rm B}$) for each candidate
being a high-$z$ quasar, following the recipe provided by Mortlock et al.
(2012), using the matched HSC $i$-, $z$-, $y$-band and near-IR magnitudes. The
calculation considers flux upper limits in the HSC bands, while near-IR
magnitudes are used only when a source is detected in the given band. Our
algorithm includes models of high-$z$ quasars and Galactic cool stars and
brown dwarfs, taking into account their spectral energy distributions (SEDs)
and surface densities as a function of apparent magnitude and Galactic
coordinates. We select all the candidates with $P_{\rm Q}^{\rm B}>0.1$, and
also keep a fraction of the remaining sources (the “low-$P_{\rm Q}^{\rm B}$
sample” hereafter; see below), for the subsequent selection.

  4. 4.

All the pre-stacked and stacked images of the candidates are retrieved from
the HSC-SSP database, and screened by an automatic algorithm based on Source
Extractor (Bertin & Arnouts, 1996) and by visual inspection. This step removes
numerous false detections missed by the catalog quality flags, such as cosmic
rays and detector artifacts, as well as variable sources.

  5. 5.

The candidates are fed into follow-up spectroscopy programs at the 8.2-m
Subaru Telescope and the 10.4-m Gran Telescopio Canarias (GTC). We use the
Faint Object Camera and Spectrograph (FOCAS; Kashikawa et al., 2002) on Subaru
to observe the wavelength range 0.75 – 1.0 $\mu$m with the VPH900 grism and
1″.0 slits, giving a spectral resolution of $R\sim 1200$ (Program ID:
S18B-011I). Similarly, the Optical System for Imaging and low-intermediate-
Resolution Integrated Spectroscopy (OSIRIS; Cepa et al., 2000) on GTC is used
with the R2500I grism and 1″.0 longslit, yielding spectra over 0.75 – 1.0
$\mu$m with $R\sim 1500$ (Program IDs: GTC5-20A, GTC10-20B, GTC42-21B). The
objects presented in this paper were observed mostly in gray nights under both
photometric and non-photometric sky conditions, with a typical seeing of 0″.6
– 1″.2.

We have so far completed spectroscopy of all but the faintest candidates drawn
from $\sim$1200 deg2 of the HSC-SSP public data release 3 (PDR3; Aihara et
al., 2021). The remaining candidates are either (i) $i$-dropouts with $z_{\rm
AB}>24.0$ or without $y$-band detections, or (ii) $i$-dropouts with $z_{\rm
AB}>23.5$ and $i_{\rm AB}-z_{\rm AB}<2.0$. All the $z$-dropout candidates have
been observed; while the formal magnitude cut is $y_{\rm AB}=25.0$ (Step 1),
the actual limiting magnitude depends mostly on the depth achieved in the HSC
imaging, which is $y_{\rm AB}\sim 24.4$ for 5$\sigma$ detection of point
sources in the Wide layer (Aihara et al., 2021). This paper presents
spectroscopic identification of 108 candidates, observed over the past two
years since our previous discovery paper (Matsuoka et al., 2019a).

##  3 Results and Discussion

Table 1 is the journal of discovery spectroscopy, including the coordinates
and photometric information of the observed candidates. The objects detected
in the near-IR bands are listed in Table 2. The 108 candidates include 69
quasars at $5.8<z<7.0$, seven galaxies at $5.6<z<6.7$, an [O III] emitter at
$z=0.954$, and 31 cool stars and brown dwarfs in the Milky Way. Figures 1 – 7
present their reduced spectra, in the same order as in Table 1. The spectra
have been scaled in flux to match the HSC magnitudes in the $z$/$y$ bands for
$i$-/$z$-dropouts. We found clear trace of signals in both the 2d and 1d
spectra of all the presented objects.

The classification and measurements of the spectra are performed in a way
consistent with our previous papers. The 69 objects in Figures 1 – 5 (top
panels) are classified as high-$z$ quasars based on the broad Ly$\alpha$ line,
blue rest-frame ultraviolet continuum, and/or sharp continuum break just
blueward of Ly$\alpha$. Seven high-$z$ objects lacking AGN signatures are
classified as galaxies (Figure 5 middle panels). The 69 quasars include five
type-II candidates ($J225209.17+040243.8$, $J125845.66-004757.5$,
$J104429.18+010207.1$, $J120253.13+025630.8$, and $J110746.24+041101.2$) with
very luminous ($>10^{43}$ erg s-1) and narrow (full width at half maximum
[FWHM] $<$ 500 km s-1) Ly$\alpha$ emission. Such Ly$\alpha$ features are often
associated with active galactic nuclei (AGNs) in the lower-$z$ Universe (e.g.,
Alexandroff et al., 2013; Konno et al., 2016; Sobral et al., 2018; Spinoso et
al., 2020). Indeed, our deep Keck/MOSFIRE spectroscopy of a similar object
from SHELLQs has revealed very strong C IV $\lambda$1549 doublet lines,
demonstrating that it is an AGN (Onoue et al., 2021b). Past surveys of
high-$z$ Ly$\alpha$ emitters (LAEs) also found similar objects at the bright
end ($>10^{43}$ erg s-1) of the Ly$\alpha$ luminosity function, with a
significant contribution expected from AGNs (e.g., Santos et al., 2016; Konno
et al., 2018). However, it is currently hard to make a clear distinction
between extreme star formation, AGN, and other possibilities powering those
most luminous LAEs; future observations in other wavelengths, in particular
X-rays for AGNs, will be key to making robust classifications.

The distinction between the faint (type-I) quasars and galaxies is also
sometimes ambiguous, partly due to the limited data quality. Figure 8 presents
the composite spectra of the high-$z$ quasars in three bins of absolute
magnitudes ($M_{1450}<-24.2$, $-24.2<M_{1450}<-23.5$, and $-23.5<M_{1450}$;
type-II candidates were excluded) and of the high-$z$ galaxies, discovered in
SHELLQs so far. These spectra were generated by moving the individual spectra
to the rest frame, normalizing to the median $M_{1450}$ of each group of
objects being stacked, and then median-stacking. The 39 quasars in the lowest
luminosity bin and the 38 galaxies have similar distributions and median
values of $M_{1450}$, but the composite spectra are strikingly different; the
quasar composite shows clear broad emission lines of Ly$\alpha$ and N V
$\lambda$1240, while the galaxy composite lacks such emission features and
instead has interstellar absorption lines of Si II $\lambda$1260, Si II
$\lambda$1304, and C II $\lambda$1335\. This demonstrates that our spectral
separation between quasars and galaxies is robust as a whole, while there may
be minor cases of misclassification for individual objects.

We measured the redshift of each quasar or galaxy via the observed wavelength
of the Ly$\alpha$ line or of the onset of the IGM H I absorption. This
procedure is not always easy, due to the H I damping-wing absorption, the
ambiguity in determining the onset of the Gunn & Peterson (1965, GP) trough,
and low signal-to-noise (S/N) spectra in some cases. The uncertainty of the
present redshift measurements is thus relatively large, from $\Delta z\sim
0.01$ (when Ly$\alpha$ has a clear peak) to $\sim 0.1$ (when Ly$\alpha$
emission is not visible). The absolute magnitude ($M_{1450}$) of each object
was measured by extrapolating the observed luminosity in a continuum window,
selected at wavelengths relatively free of strong sky emission lines, by
assuming a power-law continuum model ($F_{\lambda}\propto\lambda^{\alpha}$)
with $\alpha=-1.5$ for quasars (e.g., Vanden Berk et al., 2001) or
$\alpha=-2.0$ for galaxies (e.g., Stanway et al., 2005). The Ly$\alpha$ ($+$ N
V $\lambda$1240) properties were measured with the continuum flux estimated
either on the red side of the line (for objects with relatively narrow
Ly$\alpha$) or with the above power-law continuum model (for the remaining
objects). Table 3 summarizes the results of the spectral measurements, and
Figure 9 presents the distribution of redshifts and absolute magnitudes of all
the SHELLQs objects at $z>5.6$, including those reported in our previous
papers.

Here we briefly note on a few quasars with unusual spectral features.
$J115006.96+021131.0$ ($z=6.00$) has a second continuum break at $\lambda_{\rm
obs}\simeq 9300$ Å. This break is also clear in the 2d spectra, and the HSC
color of this object ($z_{\rm AB}-y_{\rm AB}=0.64$) is considerably redder
than expected for a typical quasar at the same redshift (see Figure 11 below).
No particular feature is known at the corresponding rest-frame wavelength
($\lambda_{\rm rest}\sim 1330$ Å) in a typical quasar spectrum (e.g., Vanden
Berk et al., 2001), and thus the origin of this break is unclear. The HSC
images show no evidence of an overlapping source; the quasar is a clear point
source without significant displacement observed between the $i$-, $z$-, and
$y$-band image centroids. Nonetheless, if the second break corresponds to the
Ly$\alpha$ wavelength of a background source, its redshift would be $z\sim
6.6$. Alternatively, this feature might be caused by a broad absorption line
(BAL) of Si II $\lambda$1398 with very high blueshift velocities, $>$15,000 km
s-1. $J023551.42+013932.3$ ($z=6.02$) exhibits unambiguous features of BALs;
weaker absorption features may be present in other objects as well (e.g.,
$J110327.65+022947.2$ at $z=6.49$), but higher-quality data are necessary for
the confirmation of their presence and nature, e.g., whether they are
intrinsic to the quasars or are produced by foreground metal absorbers.
$J145537.54+035929.0$ ($z=5.93$) has significant excess flux at $\lambda_{\rm
obs}<8400$ Å in the GP trough. This is surprising, since the HSC colors
($i_{\rm AB}-z_{\rm AB}=2.1$ and $z_{\rm AB}-y_{\rm AB}=-0.4$) are perfectly
consistent with being a quasar at $z=5.9$. Indeed the color estimated from the
spectrum, $i_{\rm AB}-z_{\rm AB}<0.6$,222 An upper limit is reported here
since the spectrum only partially covers the HSC $i$-band.  conflicts with the
HSC measurement. This object is either (i) a high-$z$ quasar with an
overlapping foreground transient source that appeared after the HSC imaging
and affected only the spectroscopic observations, or (ii) a low-$z$ variable
source (however, we are not aware of any similar spectra in the literature)
which was relatively faint/bright at the time of the HSC $i$-/$z$-band
imaging, making it appear to be an $i$-dropout in broad-band photometry. We
tentatively keep this object in the quasar category for now, and will revisit
its nature with future observations. Finally, while most of our low-luminosity
quasars have no observable signal in the GP trough, the brightest ones
sometimes exhibit spikes of transmitted flux. For example,
$J021430.90+023240.4$ ($z=6.85$) and $J021847.04+000715.0$ ($z=6.78$) have
significant positive signals at $\lambda_{\rm obs}=8050-8100$ Å as displayed
in Figure 10; these signals are also apparent in the 2d spectra. The large
numbers of low-luminosity quasars will offer a unique probe of the small-scale
structure of reionization, once higher-quality spectra are obtained with
future deep observations.

Figure 11 displays the two-color diagram of all 312 objects with spectroscopic
identification reported in the past and present SHELLQs papers.333 162
high-$z$ quasars (including 23 type-II candidates), 38 high-$z$ galaxies, 17
[O III] emitters at $z=0.8-1.0$, and 95 Galactic cool stars and brown dwarfs.
The brown dwarf $J161042.47+554203.4$ presented in Matsuoka et al. (2019a) is
not found in the PDR3 source catalog for unknown reasons, and thus is not
plotted. The quasars populate the lower-right and upper portions of this
diagram and are almost absent in between ($1<z_{\rm AB}-y_{\rm AB}<2$), where
the quasar model track intersects the stellar and brown-dwarf sequence;
sources with such moderate colors can exceed $P^{\rm B}_{\rm Q}=0.1$ only when
they are very close to the quasar model track or have near-IR magnitudes that
exclude the case of Galactic dwarfs. The HSC colors of the spectroscopically-
confirmed galaxies are indistinguishable from those of the quasars, but most
of the galaxies that we select are at $z\leq 6$. This is presumably related to
the faintness of these galaxies, with magnitudes mostly around $z_{\rm
AB}=24.0$, i.e., close to the limit of our follow-up spectroscopy. They would
quickly become fainter if redshifted to $z>6$, as the observed $z$-band flux
is progressively dominated by the GP trough.

The present quasar candidates also include an [O III] emitter at $z=0.954$, as
displayed in Figure 5. The strong [O III] $\lambda$4959 and $\lambda$5007
lines in the $y$-band give this galaxy a red $z-y$ color. Table 3 reports the
measurements of the two [O III] lines, H$\gamma$, and H$\beta$. Our past
selection included many similar objects at $z\sim 0.8$, which appear as
$i$-dropouts due to the strong lines in the $z$-band. We now know that their
colors are distinct from those of high-$z$ quasars, as evident in Figure 11,
and thus we recently incorporated an additional color cut ($i-z<2.5$ and
$z-y<-1.0$, as mentioned in §2) which eliminates most such contaminants.

We have also identified 31 Galactic cool stars and brown dwarfs with the
present spectroscopy, as displayed in Figures 6 and 7. Table 4 lists the rough
spectral classes, estimated by fitting the spectral standard templates of M4-
to T8-type dwarfs (Burgasser, 2014; Skrzypek et al., 2015) to the observed
spectra. We emphasize that the stellar classifications are meant to be only
approximate, given the relatively poor data quality and limited spectral
coverage. The number of Galactic dwarfs identified in SHELLQs has now grown to
96, many of which entered the sample because of inaccurate HSC photometry in
past DRs. Indeed, the majority of the dwarfs have $P^{\rm B}_{\rm Q}<0.1$ and
thus would not be selected as candidates with the magnitudes from PDR3; see
Figure 11. The HSC-SSP data reduction pipeline (hscPipe; Bosch et al., 2018)
provides accurate flux measurements for the vast majority of sources, but the
high-$z$ quasars we are seeking are as rare as the very unusual cases of
erroneous photometry that happened to dwarfs. On a related note, the dwarfs we
have identified spectroscopically represent a very biased sample, since the
selection algorithm is tuned to remove typical dwarfs with correct photometry.
Figure 11 indicates that only the dwarfs closest to the quasar model track
have $P^{\rm B}_{\rm Q}>0.1$, as one would expect.444 The one exception is
$J142331.18-010618.6$ with $i_{\rm AB}-z_{\rm AB}=2.0$ and $z_{\rm AB}-y_{\rm
AB}=0.9$, which has $P^{\rm B}_{\rm Q}=1.0$ because of unexpectedly faint
near-IR magnitudes given the HSC magnitudes.  Finally, given the limited data
quality, we cannot exclude the possibility that some of these objects actually
belong to extragalactic populations, e.g., compact and quiescent galaxies at
$z\sim 1$ which have similar colors to Galactic dwarfs; a further
investigation on this issue requires much deeper observations than presented
here.

The above tables and figures include 16 objects from our first set of
spectroscopy of the low-$P^{\rm B}_{\rm Q}$ sample, which are deliberately
selected from the sources with $P^{\rm B}_{\rm Q}<0.1$ (see Step 3 of the
selection flow in §2). Together with the main spectroscopic program for the
$P^{\rm B}_{\rm Q}>0.1$ candidates, these additional observations have
completed the identification of PDR3 point sources with ($z_{\rm AB}<24.0$,
$\sigma_{z}<0.155$, $i_{\rm AB}-z_{\rm AB}>2.0$, $z_{\rm AB}-y_{\rm AB}<0.5$,
and $y$-band detection; $i$-dropouts) across the entire Wide layer, and those
with ($y_{\rm AB}<24.0$, $\sigma_{y}<0.155$, and $z_{\rm AB}-y_{\rm AB}>2.0$;
$z$-dropouts) in the Spring fields (RA = 8h – 17h) of the Wide layer.555 In
other words, there are only 16 objects that satisfy these color cuts and have
$P^{\rm B}_{\rm Q}<0.1$ over the above fields. We found that the 16 targets
include three quasars at $z=6.55-6.63$ ($J091906.33+051235.3$,
$J144045.91+001912.9$, and $J145005.39-014438.9$) and 13 Galactic dwarfs. The
redshift $z=6.6$ corresponds to the quasar color $z_{\rm AB}-y_{\rm AB}\sim
2.0$, a boundary between the $P^{\rm B}_{\rm Q}>0.1$ and $<0.1$ regions of the
two-color diagram (Figure 11), so discovery of the three quasars is perfectly
consistent with what one would expect. We see no evidence of significant
incompleteness in the Bayesian selection compared to the simple color cuts.

As previously mentioned, a significant fraction of the contaminants in our
spectroscopic sample comes from inaccurate HSC photometry in earlier DRs. A
number of factors have contributed to the continuous improvement of the
photometry, including the additional exposures of the same fields and the
updated algorithms of hscPipe for better treatments of, e.g., sky subtraction,
removal of scattered light and artifacts, photometric calibration, and object
detection (Bosch et al., 2018; Aihara et al., 2019, 2021). If we had started
the SHELLQs project with PDR3 photometry, the success rate of follow-up
spectroscopy would have been much higher. Out of the 312 spectroscopically-
identified objects plotted in Figure 11, 205 pass our latest selection with
the PDR3 photometry. Of the 205 objects, 154 are high-$z$ quasars (including
22 type-II candidates)666 Figure 11 clarifies what happened to the remaining
eight quasars; three are too blue ($i_{\rm AB}-z_{\rm AB}<1.5$) to pass the
color cuts in Step 1 of the selection, and five have $P_{\rm Q}^{\rm B}<0.1$
because of their colors relatively close to those of Galactic dwarfs.  and 33
are galaxies, amounting to fractions of 75 % (64 % if the type-II candidates
are excluded) and 16 %, respectively. Thus 91 % of the photometric candidates
lie at $z>5.6$. The [O III] emitters make a negligible contribution (3
objects, 1 %), while the contamination rate of Galactic dwarfs is 7 % (15
objects). Thus our selection algorithm has very high efficiency, even though
we are probing an unprecedentedly low-luminosity population of quasars.

We are approaching the end of the HSC-SSP survey; as of Nov 2021, the survey
has observed for 325 of the allocated 330 nights. PDR3 includes the reduced
data from 278 nights, and the spectroscopic identification of all but the
faintest high-$z$ quasar candidates from the data have been reported in the
previous and present SHELLQs papers. The remaining candidates will be covered
in our forthcoming observations, and eventually, an SSP survey planned with
the Subaru Prime Focus Spectrograph (PFS) under development (Takada et al.,
2014; Tamura et al., 2016, 2018) will provide the opportunity to observe a
broader range of candidates, e.g., very faint ($z_{\rm AB}>24.5$) or extended
$i$-dropouts. We aim to start the PFS-SSP survey in 2023.

The new discoveries reported here represent a significant increase in the size
of the SHELLQs sample. Our next goals are to tighten the constraints on the
luminosity function (LF) at $z=6$ (Matsuoka et al., 2018c) and measure the LF
at $z=7$. Diverse follow-up projects are also ongoing, including near-zone
size measurements (e.g., Ishimoto et al., 2020, T.-Y. Lu et al., in prep.),
clustering analyses, and characterization of the optical discovery spectra (A.
Takahashi et al., in prep.) and near-IR broadband SEDs (e.g., Kato et al.,
2020), as well as the two key projects with near-IR spectrographs and ALMA
described in §1. Further ambitious programs have been approved and await
observations, including those with Chandra and James Webb Space Telescope
(Onoue et al., 2021a) to study SHELLQs objects in greater detail.

This research is based on data collected at the Subaru Telescope, which is
operated by the National Astronomical Observatory of Japan. We are honored and
grateful for the opportunity of observing the Universe from Maunakea, which
has the cultural, historical and natural significance in Hawaii. We appreciate
the staff members of the telescope for their support during our FOCAS
observations. The data analysis was in part carried out on the open use data
analysis computer system at the Astronomy Data Center of NAOJ. This work is
also based on observations made with the GTC, installed at the Spanish
Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de
Canarias, on the island of La Palma. We thank Stefan Geier and other support
astronomers for their help during preparation and execution of our observing
program. Y. M. was supported by the Japan Society for the Promotion of Science
(JSPS) KAKENHI Grant No. JP17H04830, No. 21H04494, and the Mitsubishi
Foundation grant No. 30140. K. I. acknowledges support by the Spanish MCIN
under grant PID2019-105510GB-C33/AEI/10.13039/501100011033 and “Unit of
excellence María de Maeztu 2020-2023” awarded to ICCUB (CEX2019-000918-M). The
HSC collaboration includes the astronomical communities of Japan and Taiwan,
and Princeton University. The HSC instrumentation and software were developed
by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute
for the Physics and Mathematics of the Universe (Kavli IPMU), the University
of Tokyo, the High Energy Accelerator Research Organization (KEK), the
Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA),
and Princeton University. Funding was contributed by the FIRST program from
the Japanese Cabinet Office, the Ministry of Education, Culture, Sports,
Science and Technology (MEXT), the Japan Society for the Promotion of Science
(JSPS), Japan Science and Technology Agency (JST), the Toray Science
Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. This paper
is based on data retrieved from the HSC data archive system, which is operated
by Subaru Telescope and Astronomy Data Center (ADC) at NAOJ. Data analysis was
in part carried out with the cooperation of Center for Computational
Astrophysics (CfCA) at NAOJ. This paper makes use of software developed for
Vera C. Rubin Observatory. We thank the Rubin Observatory for making their
code available as free software at http://pipelines.lsst.io/. The Pan-STARRS1
Surveys (PS1) and the PS1 public science archive have been made possible
through contributions by the Institute for Astronomy, the University of
Hawaii, the Pan-STARRS Project Office, the Max Planck Society and its
participating institutes, the Max Planck Institute for Astronomy, Heidelberg,
and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns
Hopkins University, Durham University, the University of Edinburgh, the
Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics,
the Las Cumbres Observatory Global Telescope Network Incorporated, the
National Central University of Taiwan, the Space Telescope Science Institute,
the National Aeronautics and Space Administration under grant No. NNX08AR22G
issued through the Planetary Science Division of the NASA Science Mission
Directorate, the National Science Foundation grant No. AST-1238877, the
University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos
National Laboratory, and the Gordon and Betty Moore Foundation.

Figure 1: Discovery spectra of the first set of 16 quasars, displayed in
decreasing order of redshift. The object name and the estimated redshift (with
uncertainty $\Delta z\sim 0.01-0.1$; see text) are indicated at the top left
corner of each panel, with the two asterisks indicating that the object is
noted in the text. The five type-II quasar candidates are marked with “TII”
adjacent to the redshifts. The blue dotted lines mark the expected positions
of the Ly$\alpha$ and N V $\lambda$1240 emission lines, given the redshifts.
The spectra were smoothed using inverse-variance weighted means over 3 – 13
pixels (depending on the signal-to-noise ratio [S/N]), for display purposes.
The bottom panel displays a sky spectrum, as a guide to the expected noise.
Figure 2: Same as Figure 1, but for the second set of 16 quasars.  Figure 3:
Same as Figure 1, but for the third set of 16 quasars.  Figure 4: Same as
Figure 1, but for the fourth set of 16 quasars.  Figure 5: Same as Figure 1,
but for the last set of quasars in the top five panels. The following panels
present seven galaxies and an [O III] emitter, with the expected positions of
Si II $\lambda$1260, Si II $\lambda$1304, and C II $\lambda$1335 (for the
galaxies) and of H$\gamma$, H$\beta$, and [O III] $\lambda$4959, $\lambda$5007
lines (for the [O III] emitter) marked by the dotted lines.  Figure 6: Same as
Figure 1, but for the first set of 16 Galactic cool stars and brown dwarfs,
ordered by the right ascension. The red lines represent the best-fit
templates, whose spectral types are indicated at the top left corner of the
individual panels.  Figure 7: Same as Figure 6, but for the last set of 15
Galactic dwarfs.  Figure 8: Median-stacked spectra of the high-$z$ objects
discovered by SHELLQs. The top three panels present those created from 51
quasars with $M_{1450}<-24.2$, 49 quasars with $-23.5<M_{1450}<-24.2$, and 39
quasars with $M_{1450}>-23.5$, while the bottom panel presents that created
from 38 galaxies. The median $M_{1450}$ of the stacked objects is reported in
each panel.  Figure 9: Redshifts and the rest-frame ultraviolet absolute
magnitudes ($M_{1450}$) of all the high-$z$ objects reported in the past and
present SHELLQs papers, including quasars (blue dots), type-II quasar
candidates (blue dots enclosed by larger circles), and galaxies (green dots).
We also plot all the other high-$z$ quasars published to date (gray dots),
compiled mostly from the papers referenced in §1.  Figure 10: Examples of the
transmitted fluxes in the GP trough, found along the sightlines toward
J021430.90+023240.4 (top) and J021847.04+000715.0 (bottom). The black and cyan
lines represent the observed fluxes and associated 1$\sigma$ errors,
respectively.  Figure 11: HSC $i-z$ and $z-y$ colors of the high-$z$ quasars
(blue symbols), the high-$z$ galaxies (green), the [O III] emitters at
$z=0.8-1.0$ (cyan), and Galactic cool stars and brown dwarfs (red), with
spectroscopic identification reported in the past and present SHELLQs papers;
the filled and open circles represent those with $P_{\rm Q}^{\rm B}>0.1$ and
$P_{\rm Q}^{\rm B}\leq 0.1$, respectively. The magnitudes are taken from PDR3.
The arrows represent 3$\sigma$ limits, while the objects detected only in the
$y$-band are placed at $i_{\rm AB}-z_{\rm AB}=i_{\rm AB}^{\rm lim}-z_{\rm
AB}^{\rm lim}$ with dotted error bars, where $m_{\rm AB}^{\rm lim}$ represents
the 3$\sigma$ limiting magnitude. We also plot the model colors of quasars
(solid curve) and galaxies (dashed curve) at $z\geq 5.7$, with the diamonds
marking redshifts at $\Delta z=0.1$ intervals. The gray crosses and dots
represent simulated colors of main-sequence stars and M-, L-, T-type brown
dwarfs, as indicated at the bottom-left corner (see Matsuoka et al., 2016, for
the details of those models). The hatched area represents the color cuts used
in Step 1 of the selection (see §2).

Table 1: Journal of Discovery Spectroscopy

Object | $i_{\rm AB}$ | $z_{\rm AB}$ | $y_{\rm AB}$ | $P_{\rm Q}^{\rm B}$ | $t_{\rm exp}$ | Date (Inst)
---|---|---|---|---|---|---
| (mag) | (mag) | (mag) |  | (min) |
Quasars
$J131746.92+001722.2$ |  $>$26.02 |  $>$24.77 | 22.22 $\pm$ 0.03 | 1.000 | 120 | 2020 Apr 25 & 30 (O)
$J134905.63+015608.9$ |  $>$26.00 |  $>$24.27 | 22.20 $\pm$ 0.07 | 1.000 | 120 | 2020 Mar 4 & Apr 25 (O)
$J021430.90+023240.4$ | 26.41 $\pm$ 0.44 |  $>$25.49 | 21.86 $\pm$ 0.02 | 1.000 | 120 | 2020 Sep 17 – 18 (O)
$J131050.13-005054.1$ | 27.06 $\pm$ 0.48 |  $>$25.16 | 22.55 $\pm$ 0.04 | 1.000 | 35 | 2021 Feb 21 (F)
$J021847.04+000715.0$ | 26.08 $\pm$ 0.23 |  $>$24.82 | 21.10 $\pm$ 0.01 | 1.000 | 50 | 2019 Oct 4 – 6 (F)
$J133833.25-001832.9$ | 26.40 $\pm$ 0.29 | 25.61 $\pm$ 0.24 | 22.72 $\pm$ 0.04 | 1.000 | 30 | 2020 Dec 22 (F)
$J113034.65+045013.1$ | 27.71 $\pm$ 0.88 | 26.00 $\pm$ 0.68 | 22.78 $\pm$ 0.05 | 0.972 | 25 | 2021 Jan 5 (F)
$J225209.17+040243.8$ | 26.65 $\pm$ 0.54 | 25.89 $\pm$ 0.38 | 23.12 $\pm$ 0.08 | 0.403 | 30 | 2019 Oct 4 (F)
$J091041.14+005646.3$ | 26.78 $\pm$ 0.35 | 24.41 $\pm$ 0.06 | 22.06 $\pm$ 0.02 | 1.000 | 15 | 2020 Dec 22 (F)
$J103537.74+032435.7$ |  $>$25.88 | 24.99 $\pm$ 0.24 | 22.60 $\pm$ 0.05 | 0.111 | 30 | 2021 Jan 3 (F)
$J145005.39-014438.9$ |  $>$26.27 | 25.67 $\pm$ 0.28 | 23.45 $\pm$ 0.08 | 0.003 | 30 | 2021 Feb 21 (F)
$J102314.45-004447.9$ |  $>$26.10 | 25.11 $\pm$ 0.17 | 22.08 $\pm$ 0.02 | 1.000 | 15 | 2020 Dec 22 (F)
$J091906.33+051235.3$ | 26.83 $\pm$ 0.57 | 24.47 $\pm$ 0.21 | 22.28 $\pm$ 0.05 | 0.027 | 15 | 2021 Feb 22 (F)
$J111427.15+021517.6$ | 27.20 $\pm$ 0.44 | 23.36 $\pm$ 0.04 | 21.91 $\pm$ 0.02 | 1.000 | 15 | 2021 Jan 4 (F)
$J144045.91+001912.9$ | 27.12 $\pm$ 0.55 | 25.46 $\pm$ 0.21 | 23.39 $\pm$ 0.06 | 0.006 | 60 | 2021 Feb 23 & Mar 3 (F)
$J110327.65+022947.2$ |  $>$25.97 | 23.39 $\pm$ 0.04 | 22.51 $\pm$ 0.07 | 0.910 | 15 | 2021 Jan 4 (F)
$J132539.95+441559.0$ | 25.42 $\pm$ 0.10 | 20.91 $\pm$ 0.01 | 20.92 $\pm$ 0.01 | 1.000 | 5 | 2021 Aug 16 (O)
$J132352.02-013941.4$ | 25.79 $\pm$ 0.27 | 22.85 $\pm$ 0.03 | 21.93 $\pm$ 0.03 | 1.000 | 30 | 2020 Mar 3 (O)
$J110423.75+024708.6$ | 27.13 $\pm$ 0.57 | 23.18 $\pm$ 0.03 | 22.94 $\pm$ 0.08 | 1.000 | 10 | 2021 Jan 4 (F)
$J140617.42+433033.2$ |  $>$25.36 | 23.43 $\pm$ 0.04 | 23.46 $\pm$ 0.15 | 1.000 | 90 | 2021 Aug 12 (O)
$J105131.80-015159.0$ |  $>$26.00 | 23.79 $\pm$ 0.06 | 23.35 $\pm$ 0.11 | 1.000 | 30 | 2021 Jan 4 (F)
$J133206.46-011325.7$ | 24.94 $\pm$ 0.09 | 21.87 $\pm$ 0.01 | 21.53 $\pm$ 0.02 | 1.000 | 15 | 2020 Apr 30 (O)
$J093830.24+015405.8$ | 26.99 $\pm$ 0.42 | 23.82 $\pm$ 0.06 | 23.55 $\pm$ 0.10 | 1.000 | 30 | 2021 Jan 3 (F)
$J122331.91+025721.5$ | 26.00 $\pm$ 0.15 | 22.86 $\pm$ 0.03 | 22.77 $\pm$ 0.04 | 1.000 | 30 | 2020 Mar 3 (O)
$J012235.47-003602.4$ | 24.40 $\pm$ 0.07 | 21.14 $\pm$ 0.01 | 21.35 $\pm$ 0.01 | 1.000 | 15 | 2020 Sep 18 (O)
$J001650.69+034154.1$ | 27.04 $\pm$ 0.61 | 23.33 $\pm$ 0.04 | 23.32 $\pm$ 0.06 | 1.000 | 90 | 2021 Aug 2 (O)
$J094713.88+034939.8$ | 27.12 $\pm$ 0.54 | 23.20 $\pm$ 0.04 | 24.15 $\pm$ 0.18 | 1.000 | 15 | 2021 Jan 3 (F)
$J104320.45+013104.7$ | 26.95 $\pm$ 0.50 | 22.94 $\pm$ 0.02 | 22.52 $\pm$ 0.04 | 1.000 | 25 | 2021 Feb 20 (F)
$J104311.09+011913.6$ | 26.25 $\pm$ 0.25 | 23.70 $\pm$ 0.03 | 23.85 $\pm$ 0.13 | 1.000 | 30 | 2021 Feb 20 (F)
$J132700.35+014147.7$ | 26.75 $\pm$ 0.53 | 23.50 $\pm$ 0.05 | 23.37 $\pm$ 0.08 | 1.000 | 35 | 2021 Jan 3 (F)
$J125845.66-004757.5$ | 27.32 $\pm$ 0.70 | 23.72 $\pm$ 0.05 | 23.55 $\pm$ 0.11 | 1.000 | 20 | 2021 Jan 2 (F)
$J084422.57+042353.7$ | 26.01 $\pm$ 0.25 | 22.61 $\pm$ 0.02 | 23.10 $\pm$ 0.10 | 1.000 | 15 | 2020 Dec 22 (F)
$J104429.18+010207.1$ | 26.91 $\pm$ 0.38 | 24.11 $\pm$ 0.04 | 24.13 $\pm$ 0.17 | 1.000 | 25 | 2021 Mar 3 (F)
$J104740.91+041724.3$ | 26.63 $\pm$ 0.26 | 23.09 $\pm$ 0.02 | 23.02 $\pm$ 0.07 | 1.000 | 15 | 2021 Jan 5 (F)
$J102047.40+042946.7$ | 25.15 $\pm$ 0.09 | 21.64 $\pm$ 0.01 | 21.29 $\pm$ 0.01 | 1.000 | 15 | 2020 Nov 18 (O)
$J093551.64+034847.2$ | 25.28 $\pm$ 0.08 | 22.24 $\pm$ 0.01 | 22.26 $\pm$ 0.03 | 1.000 | 15 | 2020 Nov 18 (O)
$J115924.01+020041.8$ | 27.11 $\pm$ 0.47 | 23.97 $\pm$ 0.06 | 24.64 $\pm$ 0.19 | 1.000 | 30 | 2021 Feb 20 (F)
$J011224.59-011557.3$ | 25.33 $\pm$ 0.27 | 22.38 $\pm$ 0.07 | 22.39 $\pm$ 0.04 | 1.000 | 90 | 2020 Dec 24 (F)
$J022223.74+024535.0$ | 24.72 $\pm$ 0.15 | 21.44 $\pm$ 0.01 | 21.82 $\pm$ 0.03 | 1.000 | 10 | 2020 Dec 22 (F)
$J112746.08+022231.5$ | 26.40 $\pm$ 0.22 | 23.41 $\pm$ 0.04 | 23.28 $\pm$ 0.08 | 1.000 | 30 | 2021 Jan 5 (F)
$J095139.01+021952.0$ |  $>$26.19 | 23.54 $\pm$ 0.05 | 25.79 $\pm$ 0.66 | 1.000 | 15 | 2021 Feb 21 (F)
$J001247.71+033716.9$ | 25.10 $\pm$ 0.10 | 21.37 $\pm$ 0.01 | 21.65 $\pm$ 0.01 | 1.000 | 15 | 2021 Aug 1 (O)
$J233429.70+050217.0$ | 24.68 $\pm$ 0.11 | 21.46 $\pm$ 0.02 | 21.57 $\pm$ 0.04 | 1.000 | 15 | 2021 Aug 1 (O)
$J002334.65+034223.2$ | 25.91 $\pm$ 0.19 | 22.82 $\pm$ 0.02 | 22.80 $\pm$ 0.04 | 1.000 | 30 | 2021 Aug 2 (O)
$J103734.52+003750.8$ | 26.38 $\pm$ 0.27 | 23.29 $\pm$ 0.04 | 23.66 $\pm$ 0.12 | 1.000 | 60 | 2020 Mar 3 (O)
$J102841.66+001755.9$ | 24.84 $\pm$ 0.07 | 21.87 $\pm$ 0.01 | 21.72 $\pm$ 0.02 | 1.000 | 15 | 2021 Feb 21 (F)
$J110248.67-010550.9$ | 25.05 $\pm$ 0.07 | 22.30 $\pm$ 0.01 | 22.37 $\pm$ 0.03 | 1.000 | 15 | 2021 Jan 24 (O)
$J111027.01+022800.7$ | 26.31 $\pm$ 0.25 | 22.69 $\pm$ 0.02 | 22.76 $\pm$ 0.06 | 1.000 | 15 | 2021 Jan 4 (F)
$J145520.26+031833.0$ | 25.75 $\pm$ 0.18 | 22.55 $\pm$ 0.02 | 22.60 $\pm$ 0.05 | 1.000 | 25 | 2021 Feb 20 (F)
$J110756.01-011819.0$ | 24.52 $\pm$ 0.04 | 21.77 $\pm$ 0.01 | 21.62 $\pm$ 0.02 | 1.000 | 15 | 2021 Jan 23 (O)
$J020415.74+001534.5$ | 25.42 $\pm$ 0.12 | 22.58 $\pm$ 0.02 | 22.78 $\pm$ 0.04 | 1.000 | 20 | 2020 Dec 22 (F)
$J132308.18+012619.2$ |  $>$25.45 | 23.80 $\pm$ 0.07 | 23.94 $\pm$ 0.14 | 1.000 | 20 | 2021 Jan 3 (F)
$J010718.87+002724.2$ | 25.12 $\pm$ 0.09 | 22.56 $\pm$ 0.03 | 22.58 $\pm$ 0.03 | 1.000 | 15 | 2019 Oct 4 (F)
$J120253.13+025630.8$ | 26.20 $\pm$ 0.17 | 23.66 $\pm$ 0.06 | 23.77 $\pm$ 0.10 | 1.000 | 15 | 2021 Feb 20 (F)
$J023551.42+013932.3$ | 24.46 $\pm$ 0.07 | 21.30 $\pm$ 0.01 | 21.48 $\pm$ 0.02 | 1.000 | 10 | 2020 Dec 22 (F)
$J110301.66+011845.7$ | 24.84 $\pm$ 0.07 | 22.92 $\pm$ 0.02 | 22.88 $\pm$ 0.06 | 1.000 | 15 | 2021 Feb 21 (F)
$J115006.96+021131.0$ | 24.52 $\pm$ 0.05 | 22.25 $\pm$ 0.02 | 21.61 $\pm$ 0.01 | 1.000 | 30 | 2021 Jan 2 (F)
$J110746.24+041101.2$ | 26.19 $\pm$ 0.20 | 24.02 $\pm$ 0.06 | 23.87 $\pm$ 0.14 | 0.994 | 25 | 2021 Mar 3 (F)
$J124359.03+032253.8$ | 26.24 $\pm$ 0.26 | 23.88 $\pm$ 0.06 | 23.89 $\pm$ 0.08 | 1.000 | 25 | 2021 Feb 21 (F)
$J010044.78+042211.5$ | 25.13 $\pm$ 0.15 | 22.96 $\pm$ 0.02 | 23.09 $\pm$ 0.07 | 1.000 | 45 | 2021 Aug 11 (O)
$J101505.59+000223.0$ | 24.04 $\pm$ 0.03 | 21.85 $\pm$ 0.01 | 22.15 $\pm$ 0.08 | 1.000 | 15 | 2021 Jan 24 (O)
$J091121.61+005146.1$ | 25.03 $\pm$ 0.07 | 23.30 $\pm$ 0.03 | 23.33 $\pm$ 0.05 | 1.000 | 25 | 2020 Dec 23 (F)
$J234836.96-003437.0$ | 23.88 $\pm$ 0.03 | 22.39 $\pm$ 0.02 | 22.65 $\pm$ 0.04 | 1.000 | 15 | 2019 Oct 5 (F)
$J145537.54+035929.0$ | 24.23 $\pm$ 0.06 | 22.15 $\pm$ 0.02 | 22.52 $\pm$ 0.05 | 1.000 | 25 | 2021 Feb 20 (F)
$J234901.28+005640.9$ | 24.40 $\pm$ 0.04 | 22.85 $\pm$ 0.02 | 22.82 $\pm$ 0.05 | 1.000 | 40 | 2020 Dec 22 (F)
$J131258.66+010902.1$ | 25.13 $\pm$ 0.12 | 22.98 $\pm$ 0.04 | 22.90 $\pm$ 0.09 | 1.000 | 15 | 2021 Jan 2 (F)
$J230610.54-012458.4$ | 24.62 $\pm$ 0.08 | 22.80 $\pm$ 0.04 | 22.41 $\pm$ 0.07 | 0.020 | 15 | 2019 Oct 5 (F)
$J102232.14+023041.9$ | 24.46 $\pm$ 0.06 | 22.64 $\pm$ 0.03 | 22.56 $\pm$ 0.07 | 1.000 | 15 | 2021 Jan 4 (F)
$J131732.73+012741.6$ | 23.70 $\pm$ 0.03 | 22.14 $\pm$ 0.02 | 22.09 $\pm$ 0.02 | 1.000 | 15 | 2020 May 16 (O)
Galaxies
$J132249.98+002849.4$ |  $>$25.89 |  $>$25.39 | 23.40 $\pm$ 0.08 | 1.000 | 50 | 2021 Feb 21 (F)
$J102936.55+040842.6$ | 26.36 $\pm$ 0.32 | 23.16 $\pm$ 0.04 | 22.57 $\pm$ 0.04 | 1.000 | 25 | 2021 Jan 3 (F)
$J102257.38-002608.2$ | 26.13 $\pm$ 0.25 | 24.01 $\pm$ 0.08 | 24.01 $\pm$ 0.14 | 0.912 | 25 | 2021 Mar 2 (F)
$J103553.04-010411.1$ | 26.69 $\pm$ 0.42 | 24.15 $\pm$ 0.07 | 24.30 $\pm$ 0.18 | 1.000 | 25 | 2021 Mar 3 (F)
$J095541.39+034025.0$ | 26.21 $\pm$ 0.23 | 24.09 $\pm$ 0.06 | 24.30 $\pm$ 0.16 | 1.000 | 25 | 2021 Mar 2 (F)
$J022443.33-064419.3$ | 24.96 $\pm$ 0.10 | 23.26 $\pm$ 0.05 | 23.02 $\pm$ 0.10 | 0.322 | 25 | 2019 Oct 5 (F)
$J021834.42-000426.1$ | 25.17 $\pm$ 0.10 | 23.81 $\pm$ 0.07 | 23.73 $\pm$ 0.09 | 0.381 | 30 | 2019 Oct 5 (F)
[O III] Emitter
$J020816.31+000346.7$ | 25.68 $\pm$ 0.18 |  $>$24.89 | 23.59 $\pm$ 0.07 | 0.105 | 10 | 2019 Oct 5 (F)
Cool Dwarfs
$J000241.98+021705.6$ | 25.15 $\pm$ 0.08 | 22.97 $\pm$ 0.05 | 22.72 $\pm$ 0.09 | 1.000 | 45 | 2020 Sep 19 (O)
$J010231.32+044303.4$ | 25.29 $\pm$ 0.46 | 23.28 $\pm$ 0.05 | 23.21 $\pm$ 0.12 | 0.830 | 90 | 2021 Aug 3 (O)
$J010514.82+034839.9$ |  $>$25.09 | 23.36 $\pm$ 0.05 | 22.79 $\pm$ 0.06 | 1.000 | 90 | 2021 Aug 12 (O)
$J015901.37+001043.0$ | 25.41 $\pm$ 0.10 | 24.01 $\pm$ 0.08 | 23.69 $\pm$ 0.07 | 0.000 | 60 | 2019 Oct 6 (F)
$J020446.06+021657.2$ | 24.51 $\pm$ 0.05 | 22.96 $\pm$ 0.03 | 22.72 $\pm$ 0.05 | 0.620 | 45 | 2020 Sep 20 (O)
$J021009.92-024422.0$ | 25.12 $\pm$ 0.04 | 23.16 $\pm$ 0.04 | 22.95 $\pm$ 0.05 | 1.000 | 25 | 2021 Jan 5 (F)
$J022812.09-012440.8$ |  $\cdots$ | 23.62 $\pm$ 0.04 | 23.24 $\pm$ 0.07 | 1.000 | 120 | 2020 Oct 10 (O)
$J023819.83-013259.7$ | 25.87 $\pm$ 0.29 | 24.07 $\pm$ 0.08 | 23.93 $\pm$ 0.18 | 0.019 | 70 | 2019 Oct 5 – 6 (F)
$J083313.13+005505.5$ | 25.93 $\pm$ 0.38 | 23.82 $\pm$ 0.08 | 23.36 $\pm$ 0.10 | 0.000 | 75 | 2021 Feb 22 – 23 (F)
$J092139.81+004932.0$ | 24.52 $\pm$ 0.04 | 22.67 $\pm$ 0.02 | 21.63 $\pm$ 0.01 | 0.000 | 15 | 2021 Feb 20 (F)
$J100500.97+003536.8$ | 27.07 $\pm$ 0.38 | 25.04 $\pm$ 0.15 | 22.90 $\pm$ 0.06 | 0.114 | 40 | 2020 Dec 22 (F)
$J113410.92+010951.1$ | 24.73 $\pm$ 0.05 | 23.21 $\pm$ 0.03 | 23.18 $\pm$ 0.06 | 1.000 | 25 | 2021 Feb 21 (F)
$J120457.75+005851.4$ |  $>$26.35 | 25.61 $\pm$ 0.21 | 23.55 $\pm$ 0.08 | 0.000 | 25 | 2021 Mar 2 (F)
$J120954.27-004105.7$ |  $>$26.45 | 25.91 $\pm$ 0.30 | 23.86 $\pm$ 0.10 | 0.000 | 30 | 2021 Mar 2 (F)
$J123559.91+031157.1$ |  $>$25.90 | 25.39 $\pm$ 0.26 | 23.26 $\pm$ 0.05 | 0.000 | 50 | 2021 Feb 22 (F)
$J124746.47+014812.9$ |  $>$25.99 | 25.35 $\pm$ 0.20 | 23.33 $\pm$ 0.06 | 0.000 | 25 | 2021 Feb 23 (F)
$J141128.46-014848.6$ | 27.07 $\pm$ 0.51 | 25.34 $\pm$ 0.26 | 23.14 $\pm$ 0.05 | 0.000 | 60 | 2021 Feb 22 (F)
$J142331.18-010618.6$ | 24.05 $\pm$ 0.03 | 22.01 $\pm$ 0.01 | 21.10 $\pm$ 0.01 | 1.000 | 15 | 2020 Apr 24 (O)
$J142536.16-010029.8$ | 25.05 $\pm$ 0.07 | 23.37 $\pm$ 0.04 | 23.11 $\pm$ 0.06 | 0.925 | 15 | 2021 Feb 21 (F)
$J162134.85+443104.1$ |  $>$25.83 | 24.77 $\pm$ 0.24 | 22.72 $\pm$ 0.07 | 0.001 | 15 | 2021 Feb 23 (F)
$J163105.93+432413.6$ | 26.11 $\pm$ 0.13 | 22.89 $\pm$ 0.02 | 21.83 $\pm$ 0.02 | 0.994 | 15 | 2021 Feb 20 (F)
$J220019.88+001100.9$ | 23.41 $\pm$ 0.03 | 21.25 $\pm$ 0.01 | 20.65 $\pm$ 0.02 | 0.000 | 15 | 2020 Aug 20 (O)
$J220142.44+023557.4$ | 24.48 $\pm$ 0.06 | 22.60 $\pm$ 0.03 | 21.82 $\pm$ 0.03 | 0.000 | 30 | 2020 Aug 20 (O)
$J220809.25+014202.4$ | 24.77 $\pm$ 0.05 | 22.95 $\pm$ 0.02 | 22.61 $\pm$ 0.03 | 1.000 | 45 | 2020 Sep 20 (O)
$J221417.79+010233.0$ | 25.43 $\pm$ 0.08 | 23.41 $\pm$ 0.04 | 22.73 $\pm$ 0.04 | 0.000 | 10 | 2019 Oct 5 (F)
$J223323.76+005633.7$ | 24.13 $\pm$ 0.02 | 22.34 $\pm$ 0.01 | 21.56 $\pm$ 0.01 | 0.000 | 15 | 2020 Aug 28 (O)
$J223718.63+052003.0$ | 25.82 $\pm$ 0.25 | 24.18 $\pm$ 0.08 | 24.01 $\pm$ 0.13 | 0.001 | 50 | 2019 Oct 6 (F)
$J224130.62+041820.2$ | 23.85 $\pm$ 0.03 | 22.36 $\pm$ 0.01 | 21.56 $\pm$ 0.02 | 0.000 | 15 | 2020 Aug 24 (O)
$J224538.06+010727.4$ | 24.16 $\pm$ 0.03 | 22.61 $\pm$ 0.02 | 21.89 $\pm$ 0.02 | 0.000 | 30 | 2020 Aug 20 (O)
$J224540.11+054300.0$ | 24.17 $\pm$ 0.06 | 22.57 $\pm$ 0.02 | 21.98 $\pm$ 0.03 | 0.000 | 23 | 2020 Aug 20 (O)
$J225149.04-011009.0$ | 25.29 $\pm$ 0.18 | 23.42 $\pm$ 0.08 | 23.40 $\pm$ 0.11 | 0.490 | 90 | 2020 Sep 18 (O)

Note. — Coordinates are at J2000.0, and magnitude upper limits are placed at
$5\sigma$ significance. We took magnitudes from the HSC-SSP PDR3, corrected
for Galactic extinction, and recalculated $P_{\rm Q}^{\rm B}$ for objects
selected from earlier DRs. $J022812.09-012440.8$ has a significantly
($>5\sigma$) negative $i$-band flux record in the database, for unknown
reasons (though it is clearly detected on the image), and thus $i_{\rm AB}$ is
not reported. The column “$t_{\rm exp}$” reports the total exposure time for
each obejct. The instrument (Inst) “F” and “O” denote Subaru/FOCAS and
GTC/OSIRIS, respectively.

Table 2: Objects detected in the near-IR bands  Name | $J_{\rm AB}$ | $H_{\rm AB}$ | $K_{\rm AB}$ | Camera
---|---|---|---|---
| (mag) | (mag) | (mag) |
Quasars
$J131050.13-005054.1$ |  $\cdots$ | 21.31 $\pm$ 0.22 |  $\cdots$ | VIRCAM
$J091041.14+005646.3$ | 22.01 $\pm$ 0.22 |  $\cdots$ | 21.92 $\pm$ 0.43 | VIRCAM
$J111427.15+021517.6$ | 21.92 $\pm$ 0.22 | 21.64 $\pm$ 0.28 | 21.17 $\pm$ 0.22 | VIRCAM
$J144045.91+001912.9$ |  $\cdots$ |  $\cdots$ | 21.72 $\pm$ 0.32 | VIRCAM
$J132352.02-013941.4$ | 22.36 $\pm$ 0.35 | 21.25 $\pm$ 0.20 |  $\cdots$ | VIRCAM
$J133206.46-011325.7$ | 21.08 $\pm$ 0.09 | 20.47 $\pm$ 0.16 | 19.88 $\pm$ 0.08 | VIRCAM
$J012235.47-003602.4$ | 21.34 $\pm$ 0.23 |  $\cdots$ |  $\cdots$ | VIRCAM
$J104320.45+013104.7$ | 21.95 $\pm$ 0.25 |  $\cdots$ | 20.99 $\pm$ 0.18 | VIRCAM
$J102047.40+042946.7$ | 21.04 $\pm$ 0.22 |  $\cdots$ |  $\cdots$ | WFCAM
$J111027.01+022800.7$ | 22.25 $\pm$ 0.28 |  $\cdots$ |  $\cdots$ | VIRCAM
$J110756.01-011819.0$ | 21.94 $\pm$ 0.21 |  $\cdots$ |  $\cdots$ | VIRCAM
$J023551.42+013932.3$ |  $\cdots$ | 20.37 $\pm$ 0.23 | 19.99 $\pm$ 0.17 | WFCAM
$J115006.96+021131.0$ | 21.47 $\pm$ 0.16 | 20.68 $\pm$ 0.16 | 20.34 $\pm$ 0.11 | VIRCAM
$J131732.73+012741.6$ | 21.87 $\pm$ 0.25 |  $\cdots$ |  $\cdots$ | VIRCAM
Cool Dwarfs
$J092139.81+004932.0$ | 20.43 $\pm$ 0.07 | 19.27 $\pm$ 0.04 | 18.72 $\pm$ 0.03 | VIRCAM
$J113410.92+010951.1$ | 22.05 $\pm$ 0.22 |  $\cdots$ | 20.97 $\pm$ 0.18 | VIRCAM
$J120457.75+005851.4$ | 21.99 $\pm$ 0.24 |  $\cdots$ |  $\cdots$ | VIRCAM
$J123559.91+031157.1$ | 21.41 $\pm$ 0.18 |  $\cdots$ |  $\cdots$ | VIRCAM
$J124746.47+014812.9$ | 21.58 $\pm$ 0.16 |  $\cdots$ |  $\cdots$ | VIRCAM
$J141128.46-014848.6$ | 21.41 $\pm$ 0.14 |  $\cdots$ |  $\cdots$ | VIRCAM
$J142331.18-010618.6$ | 20.50 $\pm$ 0.08 |  $\cdots$ | 21.27 $\pm$ 0.25 | VIRCAM
$J220142.44+023557.4$ |  $\cdots$ | 19.86 $\pm$ 0.16 | 19.29 $\pm$ 0.08 | WFCAM
$J223323.76+005633.7$ | 20.40 $\pm$ 0.21 | 20.15 $\pm$ 0.17 | 19.97 $\pm$ 0.19 | WFCAM
$J224130.62+041820.2$ | 20.58 $\pm$ 0.26 |  $\cdots$ | 20.40 $\pm$ 0.26 | WFCAM

Table 3: Spectroscopic Properties

Name | Redshift | $M_{1450}$ | Line | EWrest | FWHM | log $L_{\rm line}$
---|---|---|---|---|---|---
|  | (mag) |  | (Å) | (km s-1) | ($L_{\rm line}$ in erg s-1)
Quasars
$J131746.92+001722.2$ | 6.94 | $-24.80\pm 0.07$ | Ly$\alpha$ | 43 $\pm$ 3 | 1300 $\pm$ 300 | 44.45 $\pm$ 0.01
$J134905.63+015608.9$ | 6.94 | $-24.83\pm 0.06$ | Ly$\alpha$ | 20 $\pm$ 1 | 1100 $\pm$ 100 | 44.15 $\pm$ 0.01
$J021430.90+023240.4$ | 6.85 | $-25.35\pm 0.04$ | Ly$\alpha$ | 9 $\pm$ 2 | 6300 $\pm$ 2100 | 44.00 $\pm$ 0.08
$J131050.13-005054.1$ | 6.82 | $-24.67\pm 0.10$ | Ly$\alpha$ | 13 $\pm$ 3 | 4100 $\pm$ 1900 | 43.89 $\pm$ 0.08
|  |  | N V | 4 $\pm$ 1 | 990 $\pm$ 470 | 43.42 $\pm$ 0.08
$J021847.04+000715.0$ | 6.78 | $-25.73\pm 0.02$ | Ly$\alpha$ | 27 $\pm$ 2 | 16000 $\pm$ 5000 | 44.60 $\pm$ 0.03
$J133833.25-001832.9$ | 6.70 | $-23.99\pm 0.07$ | Ly$\alpha$ | 24 $\pm$ 3 | 1300 $\pm$ 500 | 43.87 $\pm$ 0.04
$J113034.65+045013.1$ | 6.68 | $-23.94\pm 0.10$ | Ly$\alpha$ | 25 $\pm$ 4 | 2100 $\pm$ 1400 | 43.86 $\pm$ 0.07
$J225209.17+040243.8$ | 6.67 | $-24.02\pm 0.09$ | Ly$\alpha$ | 12 $\pm$ 1 |  $<$ 230 | 43.48 $\pm$ 0.03
$J091041.14+005646.3$ | 6.65 | $-24.55\pm 0.05$ | Ly$\alpha$ | 31 $\pm$ 2 | 1300 $\pm$ 1400 | 44.21 $\pm$ 0.03
$J103537.74+032435.7$ | 6.63 | $-24.51\pm 0.08$ | Ly$\alpha$ | 21 $\pm$ 4 | 7400 $\pm$ 800 | 44.02 $\pm$ 0.08
$J145005.39-014438.9$ | 6.63 | $-23.73\pm 0.09$ | Ly$\alpha$ | 12 $\pm$ 1 | 900 $\pm$ 300 | 43.48 $\pm$ 0.04
$J102314.45-004447.9$ | 6.63 | $-24.47\pm 0.08$ | Ly$\alpha$ | 33 $\pm$ 5 | 4000 $\pm$ 2200 | 44.19 $\pm$ 0.06
$J091906.33+051235.3$ | 6.62 | $-23.98\pm 0.19$ | Ly$\alpha$ | 46 $\pm$ 12 | 6800 $\pm$ 1900 | 44.14 $\pm$ 0.08
$J111427.15+021517.6$ | 6.55 | $-24.75\pm 0.08$ | Ly$\alpha$ | 35 $\pm$ 4 | 9000 $\pm$ 300 | 44.32 $\pm$ 0.05
$J144045.91+001912.9$ | 6.55 | $-23.23\pm 0.13$ | Ly$\alpha$ | 7 $\pm$ 2 | 1600 $\pm$ 600 | 43.05 $\pm$ 0.08
$J110327.65+022947.2$ | 6.49 | $-24.18\pm 0.07$ | Ly$\alpha$ | 52 $\pm$ 6 | 5400 $\pm$ 7100 | 44.27 $\pm$ 0.04
$J132539.95+441559.0$ | 6.45 | $-25.95\pm 0.17$ | Ly$\alpha$ | 78 $\pm$ 14 | 7500 $\pm$ 4100 | 45.17 $\pm$ 0.03
$J132352.02-013941.4$ | 6.44 | $-24.62\pm 0.04$ | Ly$\alpha$ | 36 $\pm$ 2 | 6800 $\pm$ 1800 | 44.29 $\pm$ 0.02
$J110423.75+024708.6$ | 6.41 | $-24.06\pm 0.08$ | Ly$\alpha$ | 41 $\pm$ 4 | 1800 $\pm$ 800 | 44.12 $\pm$ 0.04
$J140617.42+433033.2$ | 6.39 | $-23.75\pm 0.17$ | Ly$\alpha$ | 48 $\pm$ 11 | 9900 $\pm$ 100 | 44.07 $\pm$ 0.07
$J105131.80-015159.0$ | 6.34 | $-23.41\pm 0.11$ | Ly$\alpha$ | 24 $\pm$ 4 | 2800 $\pm$ 2200 | 43.62 $\pm$ 0.06
$J133206.46-011325.7$ | 6.31 | $-25.03\pm 0.07$ | Ly$\alpha$ | 48 $\pm$ 5 | 6000 $\pm$ 5000 | 44.57 $\pm$ 0.03
$J093830.24+015405.8$ | 6.31 | $-22.91\pm 0.15$ | Ly$\alpha$ | 70 $\pm$ 12 | 300 $\pm$ 360 | 43.90 $\pm$ 0.05
$J122331.91+025721.5$ | 6.27 | $-24.26\pm 0.26$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J012235.47-003602.4$ | 6.26 | $-25.08\pm 0.09$ | Ly$\alpha$ | 120 $\pm$ 10 | 2000 $\pm$ 1600 | 45.00 $\pm$ 0.02
$J001650.69+034154.1$ | 6.26 | $-23.64\pm 0.09$ | Ly$\alpha$ | 33 $\pm$ 5 | 4600 $\pm$ 300 | 43.86 $\pm$ 0.06
$J094713.88+034939.8$ | 6.25 | $-22.77\pm 0.14$ | Ly$\alpha$ | 150 $\pm$ 20 | 750 $\pm$ 350 | 44.19 $\pm$ 0.01
$J104320.45+013104.7$ | 6.25 | $-24.19\pm 0.07$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J104311.09+011913.6$ | 6.23 | $-22.73\pm 0.27$ | Ly$\alpha$ | 81 $\pm$ 22 | 3200 $\pm$ 1000 | 43.90 $\pm$ 0.04
$J132700.35+014147.7$ | 6.23 | $-23.36\pm 0.15$ | Ly$\alpha$ | 33 $\pm$ 8 | 5100 $\pm$ 800 | 43.76 $\pm$ 0.08
$J125845.66-004757.5$ | 6.22 | $-22.99\pm 0.11$ | Ly$\alpha$ | 34 $\pm$ 7 | 220 $\pm$ 150 | 43.70 $\pm$ 0.03
$J084422.57+042353.7$ | 6.21 | $-23.55\pm 0.05$ | Ly$\alpha$ | 105 $\pm$ 5 | 590 $\pm$ 70 | 44.34 $\pm$ 0.01
$J104429.18+010207.1$ | 6.20 | $-23.29\pm 0.07$ | Ly$\alpha$ | 11 $\pm$ 2 | 370 $\pm$ 420 | 43.16 $\pm$ 0.08
$J104740.91+041724.3$ | 6.19 | $-23.43\pm 0.07$ | Ly$\alpha$ | 52 $\pm$ 6 | 7900 $\pm$ 2800 | 43.97 $\pm$ 0.04
$J102047.40+042946.7$ | 6.18 | $-25.36\pm 0.02$ | Ly$\alpha$ | 14 $\pm$ 1 | 6400 $\pm$ 900 | 44.18 $\pm$ 0.04
$J093551.64+034847.2$ | 6.16 | $-24.53\pm 0.03$ | Ly$\alpha$ | 24 $\pm$ 2 | 4600 $\pm$ 600 | 44.08 $\pm$ 0.03
$J115924.01+020041.8$ | 6.15 | $-22.31\pm 0.12$ | Ly$\alpha$ | 57 $\pm$ 7 | 810 $\pm$ 460 | 43.58 $\pm$ 0.02
$J011224.59-011557.3$ | 6.14 | $-23.83\pm 0.05$ | Ly$\alpha$ | 98 $\pm$ 7 | 12600 $\pm$ 7700 | 44.39 $\pm$ 0.02
$J022223.74+024535.0$ | 6.14 | $-24.91\pm 0.04$ | Ly$\alpha$ | 78 $\pm$ 4 | 1100 $\pm$ 3800 | 44.74 $\pm$ 0.01
$J112746.08+022231.5$ | 6.13 | $-23.22\pm 0.09$ | Ly$\alpha$ | 21 $\pm$ 3 | 4200 $\pm$ 400 | 43.52 $\pm$ 0.06
$J095139.01+021952.0$ | 6.12 | $-21.53\pm 0.77$ | Ly$\alpha$ | 340 $\pm$ 240 | 1400 $\pm$ 700 | 44.04 $\pm$ 0.02
$J001247.71+033716.9$ | 6.12 | $-25.14\pm 0.06$ | Ly$\alpha$ | 97 $\pm$ 33 | 1300 $\pm$ 500 | 44.72 $\pm$ 0.03
$J233429.70+050217.0$ | 6.12 | $-25.15\pm 0.02$ | Ly$\alpha$ | 38 $\pm$ 2 | 3100 $\pm$ 500 | 44.53 $\pm$ 0.02
$J002334.65+034223.2$ | 6.12 | $-24.00\pm 0.04$ | Ly$\alpha$ | 29 $\pm$ 3 | 7300 $\pm$ 300 | 43.96 $\pm$ 0.04
$J103734.52+003750.8$ | 6.11 | $-22.93\pm 0.06$ | Ly$\alpha$ | 97 $\pm$ 6 | 820 $\pm$ 250 | 44.05 $\pm$ 0.01
$J102841.66+001755.9$ | 6.10 | $-24.94\pm 0.02$ | Ly$\alpha$ | 14 $\pm$ 2 | 14100 $\pm$ 1700 | 44.00 $\pm$ 0.05
$J110248.67-010550.9$ | 6.07 | $-24.00\pm 0.05$ | Ly$\alpha$ | 72 $\pm$ 5 | 4900 $\pm$ 2500 | 44.34 $\pm$ 0.02
$J111027.01+022800.7$ | 6.07 | $-23.56\pm 0.09$ | Ly$\alpha$ | 84 $\pm$ 9 | 11000 $\pm$ 2900 | 44.23 $\pm$ 0.03
$J145520.26+031833.0$ | 6.06 | $-23.82\pm 0.05$ | Ly$\alpha$ | 43 $\pm$ 3 | 5600 $\pm$ 1100 | 44.04 $\pm$ 0.03
$J110756.01-011819.0$ | 6.06 | $-25.11\pm 0.08$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J020415.74+001534.5$ | 6.05 | $-24.16\pm 0.03$ | Ly$\alpha$ | 16 $\pm$ 2 | 610 $\pm$ 80 | 43.76 $\pm$ 0.05
$J132308.18+012619.2$ | 6.03 | $-22.96\pm 0.09$ | Ly$\alpha$ | 7 $\pm$ 1 | 1400 $\pm$ 200 | 42.95 $\pm$ 0.08
$J010718.87+002724.2$ | 6.03 | $-23.99\pm 0.03$ | Ly$\alpha$ | 28 $\pm$ 1 | 5100 $\pm$ 900 | 43.94 $\pm$ 0.02
$J120253.13+025630.8$ | 6.02 | $-22.78\pm 0.14$ | Ly$\alpha$ | 28 $\pm$ 4 | 240 $\pm$ 180 | 43.56 $\pm$ 0.03
$J023551.42+013932.3$ | 6.02 | $-25.58\pm 0.02$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J110301.66+011845.7$ | 6.00 | $-23.53\pm 0.08$ | Ly$\alpha$ | 39 $\pm$ 12 | 1700 $\pm$ 600 | 43.74 $\pm$ 0.04
$J115006.96+021131.0$ | 6.00 | $-24.57\pm 0.07$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J110746.24+041101.2$ | 5.99 | $-23.18\pm 0.10$ | Ly$\alpha$ | 15 $\pm$ 2 | 400 $\pm$ 60 | 43.20 $\pm$ 0.04
$J124359.03+032253.8$ | 5.97 | $-22.25\pm 0.20$ | Ly$\alpha$ | 77 $\pm$ 17 | 6300 $\pm$ 400 | 43.68 $\pm$ 0.05
$J010044.78+042211.5$ | 5.96 | $-23.73\pm 0.05$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J101505.59+000223.0$ | 5.95 | $-24.13\pm 0.05$ | Ly$\alpha$ | 126 $\pm$ 7 | 15000 $\pm$ 1200 | 44.62 $\pm$ 0.01
$J091121.61+005146.1$ | 5.94 | $-23.17\pm 0.07$ | Ly$\alpha$ | 50 $\pm$ 5 | 1460 $\pm$ 50 | 44.02 $\pm$ 0.02
$J234836.96-003437.0$ | 5.94 | $-24.05\pm 0.03$ | Ly$\alpha$ | 45 $\pm$ 2 | 830 $\pm$ 420 | 44.13 $\pm$ 0.01
|  |  | N V | 36 $\pm$ 2 | 5100 $\pm$ 2100 | 44.02 $\pm$ 0.02
$J145537.54+035929.0$ | 5.93 | $-24.40\pm 0.05$ | Ly$\alpha$ | 47 $\pm$ 4 | 1900 $\pm$ 1400 | 44.32 $\pm$ 0.04
$J234901.28+005640.9$ | 5.92 | $-23.79\pm 0.06$ | Ly$\alpha$ | 15 $\pm$ 3 | 8000 $\pm$ 1100 | 43.60 $\pm$ 0.07
$J131258.66+010902.1$ | 5.90 | $-23.64\pm 0.09$ | Ly$\alpha$ | 25 $\pm$ 4 | 6900 $\pm$ 400 | 43.74 $\pm$ 0.07
$J230610.54-012458.4$ | 5.89 | $-23.92\pm 0.02$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J102232.14+023041.9$ | 5.89 | $-24.09\pm 0.04$ | Ly$\alpha$ | 15 $\pm$ 3 | 11000 $\pm$ 3500 | 43.68 $\pm$ 0.08
$J131732.73+012741.6$ | 5.88 | $-24.39\pm 0.23$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
Galaxies
$J132249.98+002849.4$ | 6.66 | $-23.69\pm 0.07$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J102936.55+040842.6$ | 6.21 | $-24.01\pm 0.07$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J102257.38-002608.2$ | 6.21 | $-23.15\pm 0.07$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J103553.04-010411.1$ | 6.09 | $-22.52\pm 0.10$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J095541.39+034025.0$ | 5.91 | $-23.05\pm 0.09$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
$J022443.33-064419.3$ | 5.69 | $-23.32\pm 0.05$ | Ly$\alpha$ |  $>$ 17 | 380 $\pm$ 20 | 42.99 $\pm$ 0.03
$J021834.42-000426.1$ | 5.68 | $-22.92\pm 0.08$ |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$
[O III] Emitters
$J020816.31+000346.7$ | 0.954 |  $\cdots$ | H$\gamma$ | 86 $\pm$ 14 |  $<$ 230 | 40.87 $\pm$ 0.03
|  |  $\cdots$ | H$\beta$ | 158 $\pm$ 35 | 220 $\pm$ 90 | 41.14 $\pm$ 0.07
|  |  $\cdots$ | [OIII] $\lambda$4959 | 271 $\pm$ 45 |  $<$ 230 | 41.38 $\pm$ 0.03
|  |  $\cdots$ | [OIII] $\lambda$5007 | 696 $\pm$ 107 |  $<$ 230 | 41.78 $\pm$ 0.02

Note. — The redshifts have uncertainties $\Delta z\sim 0.01-0.1$, depending on
the spectral features around Ly$\alpha$; see text. “EWrest” represents the
rest-frame equivalent width; 3$\sigma$ upper limits are reported for objects
without detectable continuum.

Table 4: Spectral classes of the Galactic dwarfs

Name | Class
---|---
$J000241.98+021705.6$ | M8
$J010231.32+044303.4$ | M7
$J010514.82+034839.9$ | M8
$J015901.37+001043.0$ | M8
$J020446.06+021657.2$ | L3
$J021009.92-024422.0$ | M5
$J022812.09-012440.8$ | M7
$J023819.83-013259.7$ | M5
$J083313.13+005505.5$ | L7
$J092139.81+004932.0$ | T2
$J100500.97+003536.8$ | T6
$J113410.92+010951.1$ | L2
$J120457.75+005851.4$ | T8
$J120954.27-004105.7$ | T3
$J123559.91+031157.1$ | T8
$J124746.47+014812.9$ | T5
$J141128.46-014848.6$ | T2
$J142331.18-010618.6$ | L1
$J142536.16-010029.8$ | M5
$J162134.85+443104.1$ | T6
$J163105.93+432413.6$ | T1
$J220019.88+001100.9$ | L9
$J220142.44+023557.4$ | L9
$J220809.25+014202.4$ | M8
$J221417.79+010233.0$ | M8
$J223323.76+005633.7$ | L7
$J223718.63+052003.0$ | M4
$J224130.62+041820.2$ | L8
$J224538.06+010727.4$ | M8
$J224540.11+054300.0$ | L1
$J225149.04-011009.0$ | M5

Note. — These classifications are only approximate; see text.

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