# The Cosmos in its Infancy: JADES Galaxy Candidates at $z>8$ in GOODS-S and
GOODS-N

Kevin N. Hainline Steward Observatory, University of Arizona, 933 N. Cherry
Ave, Tucson, AZ 85721, USA  Benjamin D. Johnson Center for Astrophysics $|$
Harvard & Smithsonian, 60 Garden St., Cambridge MA 02138 USA  Brant Robertson
Department of Astronomy and Astrophysics, University of California, Santa
Cruz, 1156 High Street, Santa Cruz CA 96054, USA  Sandro Tacchella Kavli
Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge
CB3 0HA, UK  Cavendish Laboratory, University of Cambridge, 19 JJ Thomson
Avenue, Cambridge CB3 0HE, UK  Jakob M. Helton Steward Observatory, University
of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Fengwu Sun Steward
Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA
Daniel J. Eisenstein Center for Astrophysics $|$ Harvard & Smithsonian, 60
Garden St., Cambridge MA 02138 USA  Charlotte Simmonds Kavli Institute for
Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK  Michael W. Topping Steward Observatory, University of Arizona,
933 N. Cherry Ave, Tucson, AZ 85721, USA  Lily Whitler Steward Observatory,
University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Christopher
N. A. Willmer Steward Observatory, University of Arizona, 933 N. Cherry Ave,
Tucson, AZ 85721, USA  Marcia Rieke Steward Observatory, University of
Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Katherine A. Suess
Department of Astronomy and Astrophysics, University of California, Santa
Cruz, 1156 High Street, Santa Cruz, CA 95064 USA  Kavli Institute for Particle
Astrophysics and Cosmology and Department of Physics, Stanford University,
Stanford, CA 94305, USA  Raphael E. Hviding Steward Observatory, University of
Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Alex J. Cameron Department
of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford
OX1 3RH, UK  Stacey Alberts Steward Observatory, University of Arizona, 933 N.
Cherry Ave, Tucson, AZ 85721, USA  William M. Baker  Kavli Institute for
Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK  Stefi Baum Department of Physics and Astronomy, University of
Manitoba, Winnipeg, MB R3T 2N2, Canada  Rachana Bhatawdekar European Space
Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo
s/n, 28692 Villanueva de la Cañada, Madrid, Spain; European Space Agency,
ESA/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, NL  Nina Bonaventura Cosmic Dawn
Center (DAWN), Copenhagen, Denmark  Niels Bohr Institute, University of
Copenhagen, Jagtvej 128, DK-2200, Copenhagen, Denmark  Steward Observatory,
University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Kristan
Boyett School of Physics, University of Melbourne, Parkville 3010, VIC,
Australia  ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions
(ASTRO 3D), Australia  Andrew J. Bunker Department of Physics, University of
Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK  Stefano
Carniani  Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa,
Italy  Stephane Charlot Sorbonne Université, CNRS, UMR 7095, Institut
d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France  Jacopo
Chevallard Department of Physics, University of Oxford, Denys Wilkinson
Building, Keble Road, Oxford OX1 3RH, UK  Zuyi Chen Steward Observatory
University of Arizona 933 N. Cherry Avenue Tucson AZ 85721, USA  Mirko Curti
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching,
Germany  Kavli Institute for Cosmology, University of Cambridge, Madingley
Road, Cambridge CB3 0HA, UK  Cavendish Laboratory, University of Cambridge, 19
JJ Thomson Avenue, Cambridge CB3 0HE, UK  Emma Curtis-Lake Centre for
Astrophysics Research, Department of Physics, Astronomy and Mathematics,
University of Hertfordshire, Hatfield AL10 9AB, UK  Francesco D’Eugenio Kavli
Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge
CB3 0HA, UK  Cavendish Laboratory, University of Cambridge, 19 JJ Thomson
Avenue, Cambridge CB3 0HE, UK  Eiichi Egami Steward Observatory, University of
Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Ryan Endsley Department of
Astronomy, University of Texas, Austin, TX 78712, USA  Ryan Hausen Department
of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St.
Baltimore, MD 21218  Zhiyuan Ji Steward Observatory, University of Arizona,
933 N. Cherry Ave, Tucson, AZ 85721, USA  Tobias J. Looser Kavli Institute for
Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK  Jianwei Lyu Steward Observatory, University of Arizona, 933 N.
Cherry Ave, Tucson, AZ 85721, USA  Roberto Maiolino Kavli Institute for
Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK  Department of Physics and Astronomy, University College London,
Gower Street, London WC1E 6BT, UK  Erica Nelson Department for Astrophysical
and Planetary Science, University of Colorado, Boulder, CO 80309, USA  Dávid
Puskás Kavli Institute for Cosmology, University of Cambridge, Madingley Road,
Cambridge CB3 0HA, UK  Cavendish Laboratory, University of Cambridge, 19 JJ
Thomson Avenue, Cambridge CB3 0HE, UK  Tim Rawle European Space Agency (ESA),
European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692
Villafranca del Castillo, Madrid, Spain  Lester Sandles Kavli Institute for
Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK  Aayush Saxena Department of Physics, University of Oxford, Denys
Wilkinson Building, Keble Road, Oxford OX1 3RH, UK  Department of Physics and
Astronomy, University College London, Gower Street, London WC1E 6BT, UK
Renske Smit Astrophysics Research Institute, Liverpool John Moores University,
146 Brownlow Hill, Liverpool L3 5RF, UK  Daniel P. Stark Steward Observatory,
University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA  Christina C.
Williams NSF’s National Optical-Infrared Astronomy Research Laboratory, 950
North Cherry Avenue, Tucson, AZ 85719, USA  Chris Willott NRC Herzberg, 5071
West Saanich Rd, Victoria, BC V9E 2E7, Canada  Joris Witstok Kavli Institute
for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge
CB3 0HE, UK

(Accepted for publication in The Astrophysical Journal, January 7, 2024)

###### Abstract

We present a catalog of 717 candidate galaxies at $z>8$ selected from 125
square arcminutes of NIRCam imaging as part of the JWST Advanced Deep
Extragalactic Survey (JADES). We combine the full JADES imaging dataset with
data from the JEMS and FRESCO JWST surveys along with extremely deep existing
observations from HST/ACS for a final filter set that includes fifteen
JWST/NIRCam filters and five HST/ACS filters. The high-redshift galaxy
candidates were selected from their estimated photometric redshifts calculated
using a template fitting approach, followed by visual inspection from seven
independent reviewers. We explore these candidates in detail, highlighting
interesting resolved or extended sources, sources with very red long-
wavelength slopes, and our highest redshift candidates, which extend to
$z_{phot}\sim 18$. Over 93% of the sources are newly identified from our deep
JADES imaging, including 31 new galaxy candidates at $z_{phot}>12$. We also
investigate potential contamination by stellar objects, and do not find strong
evidence from SED fitting that these faint high-redshift galaxy candidates are
low-mass stars. Using 42 sources in our sample with measured spectroscopic
redshifts from NIRSpec and FRESCO, we find excellent agreement to our
photometric redshift estimates, with no catastrophic outliers and an average
difference of $\langle\Delta z=z_{phot}-z_{spec}\rangle=0.26$. These sources
comprise one of the most robust samples for probing the early buildup of
galaxies within the first few hundred million years of the Universe’s history.

High-redshift galaxies(734) — James Webb Space Telescope(2291)

††facilities: JWST(NIRCam, NIRSpec), HST(ACS)††software: astropy (Astropy
Collaboration et al., 2013, 2018), matplotlib (Hunter, 2007), numpy (Harris et
al., 2020), scipy (Virtanen et al., 2020), Photutils (Bradley et al., 2023),
lenstronomy (Birrer & Amara, 2018; Birrer et al., 2021), EAZY (Brammer et al.,
2008), fsps (Conroy & Gunn, 2010).

##  1 Introduction

The earliest galaxies that appeared from the Cosmic Dark Ages fundamentally
changed the Universe. For hundreds of millions of years after recombination,
the decoupling of matter and radiation, the Universe’s baryon content
consisted of predominantly neutral hydrogen that was gravitationally pooling
and collecting, pulled by early dark matter halos. Eventually these massive
clouds collapsed and formed the first stars which gave off energetic
ultraviolet (UV) radiation, ionizing the neutral hydrogen medium throughout
the universe. Reionization is thought to have taken place across the the first
billion years after the Big Bang, but exactly how this process occurred, and
more specifically, what types of galaxies are responsible for this phase
transition, has been an active area of research for decades (Barkana & Loeb,
2001; Stark, 2016; Dayal & Ferrara, 2018; Finkelstein et al., 2019; Ouchi et
al., 2020; Robertson et al., 2023). Observations of early galaxies offer us a
vital insight into the first stages of galaxy formation and evolution, and
help us understand emergence of the elements heavier than helium. To aid in
understanding these distant sources, in this paper we present a sample of 717
galaxies and candidate galaxies with spectroscopic and photometric redshifts
corresponding to the first 200 to 600 Myr after the Big Bang and describe
their selection and properties.

To explore the very early universe, researchers search for galaxies at
increasingly high redshifts using deep observations from space. One of the
pioneering early universe surveys was the Hubble Space Telescope (HST) Deep
Field project (HDF, Williams et al., 1996), a set of observations at
wavelengths spanning the near-ultraviolet to near-infrared (IR). These data
provided an opportunity to explore galaxy evolution out to $z=4-5$ (Madau et
al., 1996). Following the success of the HDF, the next decades were spent
observing multiple deep fields down to unprecedented observational depths of
30 mag (AB) at optical and near-IR wavelengths. These surveys included the
Hubble Ultra-Deep Field (HUDF, Beckwith et al., 2006), HUDF09 (Bouwens et al.,
2011a), HUDF12 (Ellis et al., 2013; Koekemoer et al., 2013), the UVUDF
(Teplitz et al., 2013), the HST Great Observatories Origins Deep Survey
(GOODS, Giavalisco et al., 2004), the Cosmological Evolution Survey (COSMOS,
Scoville et al., 2007), and the Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey (CANDELS, Grogin et al., 2011; Koekemoer et al.,
2011). The Brightest of Reionizing Galaxy survey (BoRG, Trenti et al., 2011)
was a campaign to search for bright high-redshift galaxies across a wide (274
square arcminutes), but relatively shallow area. Researchers hoping to target
fainter galaxies also focused on lensing clusters, leading to the Cluster
Lensing and Supernova Survey with Hubble (CLASH, Postman et al., 2012), the
Hubble Frontier Fields (HFF, Lotz et al., 2017), and the Reionization Lensing
Cluster Survey (RELICS, Coe et al., 2019).

It has therefore been exciting to see the fruits of these observations: the
discovery of many thousands of galaxies at $z>4$ (Bunker et al., 2004, 2010;
Bouwens et al., 2011b; Lorenzoni et al., 2011; Ellis et al., 2013; McLure et
al., 2013; Oesch et al., 2013; Schenker et al., 2013; Oesch et al., 2014;
Bouwens et al., 2015; Finkelstein et al., 2015; Ishigaki et al., 2015;
Harikane et al., 2016; McLeod et al., 2016; Oesch et al., 2018; Morishita et
al., 2018; Bridge et al., 2019; Rojas-Ruiz et al., 2020; Bouwens et al., 2022;
Bagley et al., 2022; Finkelstein et al., 2023). While these sources have been
found through multiple methods, the primary method of high-redshift galaxy
selection relies on photometry alone. Neutral hydrogen within, surrounding,
and between distant galaxies serves to absorb ultraviolet radiation, leading
to what is commonly referred to as the “Lyman break” in the spectral energy
distribution (SED) at 912 Å. At redshifts above $z>5$, the increasingly
neutral hydrogen in the universe results in Lyman-$\alpha$ forest absorption
between 912Å and 1216Å, and sources at these redshifts are more commonly known
as “Lyman-$\alpha$ break” or “Lyman-$\alpha$ dropout” galaxies. By identifying
galaxies where the Lyman break and Lyman-$\alpha$ break fell between two
adjacent filters at a given redshift, these sources could be selected in large
quantities, as done initially in Guhathakurta et al. (1990) and Steidel &
Hamilton (1992). A similar approach involves fitting galaxy photometry to
simulated or observed galaxy SEDs, a method that utilizes more data than pure
color selection (Koo, 1985; Lanzetta et al., 1996; Gwyn & Hartwick, 1996;
Pello et al., 1996; Koo, 1999; Bolzonella et al., 2000). These results require
accurate template sets that span the full color space of the photometric data,
and include the effects of both dust extinction and intergalactic medium (IGM)
absorption. This template-fitting procedure is uncertain at high-redshifts
given the current lack of UV and optical SEDs for galaxies in the early
universe (for a review of selection methods for finding high-redshift
galaxies, see Stern & Spinrad, 1999; Giavalisco, 2002; Dunlop, 2013; Stark,
2016).

While both galaxy selection techniques have been used to find galaxies out to
$z\sim 10$ with HST, the reddest filter on the telescope’s Wide-Field Camera 3
(WFC3/IR) is at 1.6$\mu$m, such that potential galaxies at higher redshifts
would have their Lyman-$\alpha$ break shifted out of the wavelength range of
the instrument. Exploring the evolution of galaxies at earlier times was
limited by the availability of deep, high-resolution near- and mid-IR
observations. This changed with the launch of the James Webb Space Telescope
(JWST) in late 2021, an observatory carrying a suite of sensitive infrared
instruments behind a 6.5m primary mirror. The instruments include NIRCam
(Rieke et al., 2005), a high-resolution camera operating at $0.7-5.0$ $\mu$m
across a 9.7 square arcminute field of view, and NIRSpec (Jakobsen et al.,
2022), a spectrograph operating at similar wavelengths with a unique multi-
object shutter array capable of obtaining spectra at multiple resolutions.

In the first year of JWST science, researchers have identified scores of
candidate high-redshift galaxies at $z>8$ (Castellano et al., 2022; Naidu et
al., 2022; Harikane et al., 2023; Finkelstein et al., 2023; Leethochawalit et
al., 2023; Morishita et al., 2023; Whitler et al., 2023; Yan et al., 2023;
Donnan et al., 2023; Adams et al., 2023; Austin et al., 2023; Harikane et al.,
2023; Pérez-González et al., 2023; Atek et al., 2023). Some of these sources
have been spectroscopically confirmed at $z>8$ (Arrabal Haro et al., 2023a,
b), demonstrating the efficacy of using NIRCam for early universe
observations. It should be noted, however, that this is an imperfect science -
Arrabal Haro et al. (2023a) describe how the early bright $z\sim 16$ candidate
CEERS-93316 was spectroscopically found to be at $z_{spec}=4.9$ with strong
line emission and dust obscuration simulating the colors of a distant galaxy,
a possibility discussed in Naidu et al. (2022) and Zavala et al. (2023).

One of the largest JWST Cycle 1 extragalactic surveys by time allocation is
the JWST Advanced Deep Extragalactic Survey (JADES; Rieke & JADES
Collaboration, 2023), a GTO program that will eventually encompass 770 hours
of observations from three of the telescope’s instruments: NIRCam, NIRSpec,
and the mid-infrared instrument MIRI. These data, which focus on the GOODS-S
and GOODS-N regions of the sky, are ideal for finding and understanding the
most distant galaxies through imaging and follow-up spectroscopy. Because the
JADES target regions have been observed by multiple telescopes and instruments
across the electromagnetic spectrum, there is a rich quantity of ancillary
data for comparing with JWST images and spectroscopy.

Early JADES observations resulted in the discovery of the highest-redshift
spectroscopically-confirmed galaxy thus far, JADES-GS-z13-0
($z_{spec}=13.20^{+0.04}_{-0.07}$ )(Robertson et al., 2023; Curtis-Lake et
al., 2023). Because of NIRCam’s wavelength range and dichroic offering
simultaneous short wavelength (0.7 - 2.3 $\mu$m) and long wavelength (2.4 -
5.0 $\mu$m) images, these and other high-redshift candidates are detected in
multiple bands at wavelengths longward of the Lyman-$\alpha$ break. The high-
redshift galaxies that can be observed thanks to the wavelength coverage of
JWST are vital for exploring the potential downturn in the number density of
ultra-high-redshift ($z\gtrsim 10$) galaxies previously predicted by HST
observations alone (Oesch et al., 2018).

In this study, we present the results of a search through the first year of
JADES NIRCam imaging of the GOODS-S and GOODS-N regions for galaxy candidates
at $z>8$, where we combine the deepest HST optical and near-IR observations
with JADES NIRCam data taken across ten filters. These data are supplemented
by medium-band JWST imaging in five additional filters from both the publicly
available JWST Extragalactic Medium Survey (JEMS) (Williams et al., 2023a) and
First Reionization Epoch Spectroscopic COmplete Survey (FRESCO) (Oesch et al.,
2023) programs. We perform template fitting in order to select candidate high-
redshift candidates, capitalizing on the large number of filters at
wavelengths longer than $2\mu$m. Because of both the unparalleled HST coverage
and the mixture of medium and wide NIRCam filters present in the JADES data,
these data currently represent the best opportunity for uncovering galaxies at
$z>8$ with minimal low-redshift interlopers. The deepest portions of the JADES
dataset probe down to $5\sigma$ depths of 2.17 nJy (30.6 mag AB) at 2.7$\mu$m,
currently deeper than the other similar JWST extragalactic fields studied in
the literature. In addition, because of the FRESCO grism spectra and the JADES
NIRSpec spectroscopy, we also have a number of spectroscopic redshifts for
these sources confirming their selection, providing constraints on the
accuracy of photometric redshifts for galaxies in the early universe.

The structure of this paper is as follows. We begin by introducing the JADES
dataset used in this study, and we discuss our data reduction and photometric
and spectroscopic measurements in Section 2. In Section 3 we describe how we
estimate photometric redshifts and, from these results, select candidate
galaxies at $z>8$. We then spend the bulk of this study exploring the
resulting sample in Section 4, separating the objects into three bins:
$z=8-10$ (§4.1), $z=10-12$ (§4.2), and $z>12$ (§4.3). We then consider
candidate galaxies that fall out of our primary selection either because of
their template fits (§4.4) or their proximity to brighter sources (§4.5). We
also discuss the possibility of these sources being low-mass stars (§4.6),
describe which candidates have been included in samples previous to this study
(§4.7), and explore the impact of different galaxy template sets for
photometric redshifts (§4.8). Finally, we examine the selection and further
properties of these sources in Section 5 and conclude in Section 6. Throughout
this paper we assume the Planck Collaboration et al. (2020) cosmology with
$H_{0}=67.4$ km s-1 Mpc-1, $\Omega_{\mathrm{M}}=0.315$ and
$\Omega_{\Lambda}=0.685$. All magnitudes are provided using the AB magnitude
system (Oke, 1974; Oke & Gunn, 1983).

##  2 JADES Imaging and Photometry

JADES is a joint Guaranteed Time Observations (GTO) program between the NIRCam
and NIRSpec extragalactic GTO teams that consists of NIRCam imaging, NIRSpec
spectroscopy, and MIRI imaging across the GOODS-S (RA = 53.126 deg, DEC =
-27.802 deg) and GOODS-N (RA = 189.229, DEC = +62.238 deg) (Giavalisco et al.,
2004) fields. In this section we describe the Cycle 1 JADES observations taken
as of February 8 2023, the data reduction, and the measurement of fluxes and
spectroscopic redshifts. The full description of these observations is
provided in Eisenstein et al. (2023a).

###  2.1 Observations

In this paper we will discuss galaxy candidates selected from the NIRCam
imaging in both GOODS-S, with observations taken on UT 2022-09-29 through
2022-10-10 (Program 1180, PI:Eisenstein), and GOODS-N, with observations taken
on UT 2023-02-03 through 2023-02-07 (Program 1181, PI:Eisenstein). In
addition, a set of NIRCam parallels (9.8 square arcmin each) were observed
during NIRSpec observation PID 1210 (PI:Ferruit) on UT 2022-10-20 to
2022-10-24 within and southwest of the JADES Medium footprint in GOODS-S.
Another set of NIRCam observations (9.8 square arcmin) parallel to NIRSpec PID
1286 (PI:Ferruit) were observed on UT 2023-01-12 to 2023-01-13 to the
northwest of the JADES Deep footprint in GOODS-S. These data were partly
presented in both Robertson et al. (2023) as well as Tacchella et al. (2023),
although here we combine the full suite of JADES data observed as of February
8 2023.

The total current survey area of the JADES GOODS-S is 67 square arcminutes,
with 27 square arcminutes for the JADES Deep program, and 40 square arcminutes
for the JADES Medium program. The filters used for JADES Deep are NIRCam
F090W, F115W, F150W, F200W, F277W, F335M, F356W, F410M, and F444W
($\lambda=0.8-5.0\mu m$), while JADES Medium uses the same filters without
F335M. For the 1286 parallel, the JADES observations include the F070W filter.

The total current area of the NIRCam GOODS-N program is 58 square arcminutes.
The NIRCam filters observed for GOODS-N are F090W, F115W, F150W, F200W, F277W,
F335M, F356W, F410M, and F444W ($\lambda=0.8-5.0\mu m$). The GOODS-N
observations are separated into two portions: the northwest (NW) portion,
which covers 30.4 square arcminutes, and a southeast (SE) portion, which
covers 27.6 square arcminutes. The NW portion was taken under PID 1181
(PI:Eisenstein) with NIRCam as the prime instrument and MIRI in parallel,
while the SW portion was taken as part of the same program with NIRSpec as
prime and NIRCam in parallel.

We also include observations taken for the JWST Extragalactic Medium-band
Survey (JEMS, Williams et al., 2023a). These data, which are part of program
PID 1963 (PIs C. Williams, S. Tacchella, M. Maseda) were taken on UT
2022-10-12. For this study, we use the NIRCam data from JEMS which covers the
Ultra Deep Field (UDF, Beckwith et al., 2006) by the NIRCam A module, with the
NIRCam B module to the southwest, spanning the JADES Deep and Medium portions,
for a total area of 10.1 square arcminutes. The NIRCam observations in the
JEMS survey were taken with the F182M, F210M, F430M, F460M, and F480M filters
(Williams et al., 2023a).

We also supplement our observations with NIRCam data from the The First
Reionization Epoch Spectroscopic COmplete Survey (FRESCO, PID 1895, PI P.
Oesch). While nominally a NIRCam grism survey across GOODS-S and GOODS-N, we
use the FRESCO F182M, F210M, and F444W imaging of GOODS-S and GOODS-N to
supplement the filters available in JADES. The FRESCO area extends beyond the
JADES Deep and Medium region, and we do not select galaxies in this region due
to the lack of NIRCam filter coverage afforded by the JADES observations. We
use the FRESCO grism data as well as the NIRSpec observations from PID 1210
and 1286 to measure spectroscopic redshifts for sources within our sample.

The GOODS-S and GOODS-N regions have been the target of deep HST observations,
and we utilize existing HST/ACS and WFC3 mosaics. We use the HST/ACS mosiacs
from the Hubble Legacy Fields (HLF) v2.0 for GOODS-S and v2.5 for GOODS-N
($25^{\prime}\times 25^{\prime}$ for GOODS-S, and $20.5^{\prime}\times
20.5^{\prime}$ for GOODS-N, Illingworth et al., 2013; Whitaker et al., 2019).
We use data in the HST/ACS F435W, F606W, F775W, F814W, and F850LP filters.

###  2.2 Data Reduction

####  2.2.1 JADES NIRCam

The data reduction techniques used in this present study will be fully
described in a future paper (Tacchella et al. in prep), but they follow the
methods outlined in Robertson et al. (2023) and Tacchella et al. (2023), which
we briefly summarize here. For both the JADES GOODS-S and GOODS-N
observations, the data were first reduced using the JWST calibration pipeline
v1.9.2, with the JWST Calibration Reference Data System (CRDS) context map
1039. The raw images (uncal frames) are processed using the default JWST Stage
1 pipeline, which performs the detector-level corrections and results in
count-rate images (rate frames).

The JWST pipeline Stage 2 involves flat fielding and flux calibration, and was
run largely with the default values. We convert from counts/s to MJy/sr
following Boyer et al. (2022). During the data reduction, we discovered that
the current long wavelength flats used in the JWST pipeline result in non-
astrophysical artifacts in the final mosaics. To mitigate this effect, we
developed our own sky-flats, stacking in each filter 80 - 200 source-masked
raw uncal frames from across PID 1180, 1210, 1286, and JEMS. For F335M and
F410M, where we did not have enough exposures to properly perform this
stacking procedure, we instead constructed these sky flats via interpolation
using the other wide-band LW sky flats.

After Stage 2, we used custom corrections for common features seen in
JWST/NIRCam data (Rigby et al., 2023). We fit and subtracted the 1/f noise
(Schlawin et al., 2020) assuming a parametric model. To fit for the scattered-
light “wisps” in the NIRCam SW channel we constructed templates by stacking
our images from the JADES program (PID 1180, 1210, 1286) as well as other
publicly available programs (PIDs 1063, 1345, 1837, and 2738), and then
subtracted these scaled templates for the SW channel detectors A3, A4, B3, and
B4 (Tacchella et al. in prep). The background was removed using the photutils
Background2D class (Bradley et al., 2023).

We created our final mosaics using the JWST Pipeline Stage 3, after performing
an astrometric alignment using a custom version of the JWST TweakReg software.
In both GOODS-S and GOODS-N, we calculated the relative and absolute
astrometric corrections for the individual images grouped by visit and by
photometric band. We matched to sources in a reference catalog created from
HST F814W and HST F160W mosaics with astrometry tied to Gaia-EDR3 (Gaia
Collaboration et al., 2021, private communication from G. Brammer). Following
this alignment, we performed the default steps of Stage 3 of the JWST pipeline
for each filter and visit. For our final mosaics we chose a pixel scale of
0.03 arcsec/pixel and drizzle parameter of pixfrac=1 for both the SW and LW
images.

####  2.2.2 FRESCO

The FRESCO (Oesch et al., 2023) NIRCam grism spectroscopic data in the F444W
filter ($\lambda=3.9-5.0$ µm) were reduced and analyzed following the routines
in Sun et al. (2023) and Helton et al. (2023). Here we briefly summarize the
main steps of the process. Because we aim to conduct a targeted emission line
search of [O III] and H$\beta$ lines for our $z>8$ galaxy candidates, and we
do not expect any of them to have strong continuum emission that can be
detected with grism data, we used a median-filtering technique to subtract out
the remaining continuum or background on a row-by-row basis, following the
methods outlined by Kashino et al. (2023). We extracted 2D grism spectra using
the continuum-subtracted emission-line maps for all objects that are brighter
than 28.5 AB mag in the F444W band and within the FRESCO survey area. The
emission lines from sources fainter than 28.5 AB mag are not expected to be
detected with FRESCO. The FRESCO short-wavelength parallel imaging
observations were used for both astrometric and wavelength calibration of the
F444W grism spectroscopic data.

We extracted 1D spectra from the 2D grism spectra using the optimal extraction
algorithm (Horne, 1986) using the light profiles of sources in the F444W
filter. We then performed automatic identifications of $>3\sigma$ peaks in 1D
spectra (see Helton et al., 2023), and fit these detected peaks with Gaussian
profiles. We tentatively assigned spectroscopic redshifts for $>3\sigma$ peaks
which minimize the difference from the estimated photometric redshifts
(Section 4.9). Visual inspection was performed on these tentative
spectroscopic redshift solutions and spurious detections caused by either
noise or contamination were removed. The final grism spectroscopic redshift
sample of JADES sources will be presented in a forthcoming paper from the
JADES collaboration.

####  2.2.3 JADES NIRSpec

In addition to FRESCO data, we discuss NIRSpec spectroscopic redshifts in
Section 4.9, and these were reduced following the same procedure as outlined
in Curtis-Lake et al. (2023), Cameron et al. (2023), Bunker et al. (2023b),
and Bunker et al. (2023a). For the present study, we are only using the
derived spectroscopic redshifts from these data.

###  2.3 Photometry

Table 1:  5$\sigma$ Photometric Depth In JADES Areas Measured in $0.2^{\prime\prime}$ Apertures (nJy)  | GOODS-S | GOODS-N
---|---|---
Instrument | Filter | JADES Deep | JADES Medium | 1210 Parallel | 1286 Parallel | SE | NW
HST/ACS | F435W | 2.33 | 10.77 | 10.9 | 10.43 | 7.75 | 9.40
HST/ACS | F606W | 3.61 | 6.96 | 6.68 | 8.72 | 9.81 | 8.55
HST/ACS | F775W | 2.22 | 15.79 | 16.46 | 15.03 | 13.61 | 9.21
HST/ACS | F814W | 8.20 | 7.2 | 7.02 | 11.03 | 8.21 | 7.7
HST/ACS | F850LP | 4.28 | 17.53 | 18.58 | 19.55 | 15.23 | 17.55
JWST/NIRCam | F070W | - | - | - | 8.29 | - | -
JWST/NIRCam | F090W | 3.55 | 6.26 | 2.40 | 5.92 | 6.04 | 11.03
JWST/NIRCam | F115W | 2.93 | 5.44 | 2.27 | 5.26 | 4.51 | 8.08
JWST/NIRCam | F150W | 2.89 | 5.53 | 2.15 | 5.28 | 5.16 | 8.44
JWST/NIRCam | F182M | 8.04 | 9.53 | 10.37 | 11.29 | - | -
JWST/NIRCam | F200W | 3.01 | 5.27 | 2.37 | 4.63 | 4.66 | 7.78
JWST/NIRCam | F210M | 5.83 | 12.11 | 13.71 | 13.53 | - | -
JWST/NIRCam | F277W | 2.17 | 4.24 | 1.64 | 3.69 | 3.92 | 6.17
JWST/NIRCam | F335M | 3.64 | 3.81 | 2.86 | 6.08 | 5.7 | 9.12
JWST/NIRCam | F356W | 2.46 | 4.07 | 1.62 | 3.60 | 3.81 | 5.74
JWST/NIRCam | F410M | 3.23 | 6.43 | 2.39 | 5.60 | 6.33 | 9.524
JWST/NIRCam | F430M | 7.84 | 7.31 | - | - | - | -
JWST/NIRCam | F444W | 2.79 | 5.11 | 2.00 | 4.62 | 5.07 | 7.31
JWST/NIRCam | F460M | 10.71 | 9.61 | - | - | - | -
JWST/NIRCam | F480M | 7.98 | 6.51 | - | - | - | -

To compute the photometry from both the GOODS-S and GOODS-N mosaics in each
filter, we used the software package jades-pipeline developed by authors BR,
BDJ, and ST. We began by creating an inverse-variance-weighted stack of the
NIRCam F277W, F335M, F356W, F410M, and F444W images as an ultra-deep signal-
to-noise ratio (SNR) image. From this SNR image, jades-pipeline utilizes
software from the Photutils package to define a catalog of objects with five
contiguous pixels above a SNR of 3 (Bradley et al., 2023), creating a
segmentation map in the process.

From this catalog, we calculated circular and Kron aperture photometry on both
the JWST NIRCam mosaics as well as the 30mas pixel scale HST Legacy Fields
mosaics (Illingworth et al., 2016; Whitaker et al., 2019) for ACS F435W,
F606W, F775W, F814W, and F850LP filters. Forced photometry was performed using
a range of aperture sizes. The uncertainties we report were measured by
combining in quadrature both the Poisson noise from the source and the noise
estimated from random apertures placed throughout the image (e.g. Labbé et
al., 2005; Quadri et al., 2007; Whitaker et al., 2011). Elliptical Kron
aperture fluxes were measured using Photutils with a Kron parameter of $K=2.5$
and the default circularized radius six times larger than the Gaussian-
equivalent elliptical sizes while masking segmentation regions of any
neighboring source. We created empirical HST/ACS and JWST/NIRCam point spread
functions to estimate and apply aperture corrections assuming point source
morphologies (Z. Chen, private communication).

For this present study we will fit to the JADES “CIRC1” ($0.2^{\prime\prime}$
diameter aperture) fluxes, which reduces the background noise associated with
the use of larger apertures, and is appropriate given the typically small
sizes found for high-redshift galaxies (Shibuya et al., 2015; Curtis-Lake et
al., 2016; Robertson et al., 2023; Tacchella et al., 2023). We note that in
Section 4.1 we discuss a sample of morphologically extended sources with
photometric redshifts $z_{a}=8-9$, although these sources consist of multiple
smaller clumps, supporting the use of the smaller aperture photometry for
their selection. We also use Kron aperture fluxes to calculate some derived
parameters, such as the UV magnitude $M_{UV}$ to better encompass the full
flux from more extended sources. We estimated the 5$\sigma$ limiting flux
across both GOODS-S and GOODS-N from the $0.2^{\prime\prime}$ diameter fluxes
and uncertainties. In Table 1, we report these 5$\sigma$ limiting fluxes in
nJy for these portions of GOODS-S: JADES Deep, JADES Medium, the 1210
Parallel, and the 1286 Parallel. In addition, we report the limiting fluxes
for both the shallower NW portion of the GOODS-N field and the SE portion.
Understanding these depths is important for exploring the recovery of high-
redshift galaxies across the JADES data.

##  3 Galaxy Selection At z $>8$

Our final photometric catalogs span 20 optical and near-IR filters, including
both HST/ACS and JWST/NIRCam observations. Because of the multiple datasets
included in these catalogs, however, objects will only have coverage in a
subset of these filters, with the maximum number being in the area of the JEMS
survey in the GOODS-S region, where there is coverage in 19 filters (F070W was
only observed in the 1286 parallel, no portion of which overlaps with JEMS).
In this section we describe how we identified $z>8$ sources from the measured
line-flux catalog. Throughout this study, we will identify sources using
“JADES-GS-” or “JADES-GN-” followed by the right ascension (RA) and
declination (DEC) values in decimal degrees corresponding to the source.

As discussed in the introduction, we choose to employ template fitting in this
study due to the large quantity of available data in the JADES data set,
especially longward of the potential Lyman-$\alpha$ break for objects at
$z>8$. The rest-frame UV and optical continuum can be fit with the templates
as well, better constraining the exact redshift than with color selection
alone. In addition, potential strong optical emission lines such as
[OIII]$\lambda$5007 observed in high-redshift galaxies can boost the flux in
photometric filters, and can be modeled with template fitting. The JADES data
set includes multiple medium-band filters longward of 3$\mu$m, where these
effects can be more significant.

###  3.1 EAZY Photometric Redshifts

In order to estimate the redshifts of the GOODS-S galaxies, we used the
photometric redshift code EAZY (Brammer et al., 2008). EAZY combines galaxy
templates and performs a grid-search as a function of redshift. We used the
EAZY photometric redshift $z_{a}$, corresponding to the minimum $\chi^{2}$ of
the template fits, to identify high-redshift galaxies. For the fits, we
started with the EAZY “v1.3” templates, which we plot in the left panel in
Figure 1. These templates include the original seven templates modified from
Brammer et al. (2008) to include line emission, the dusty template
“c09_del_8.6_z_0.019_chab_age09.40_av2.0.dat,” and the high-equivalent-width
template taken from Erb et al. (2010) (the equivalent width of
[OIII]$\lambda$5007 measured for the galaxy this template is derived from,
Q2343-BX418, is 285 Å). We supplemented these with seven additional templates
that were designed to optimize photometric redshift estimates for mock galaxy
observations from the JAGUAR simulations (Williams et al., 2018). These
templates were created to better span the observed color space of the JAGUAR
galaxies, including both red, dusty and blue, UV-bright populations. Similar
to what has been demonstrated by other authors (e.g. Larson et al., 2023), we
found that young galaxies with very high specific star-formation rates can
have very blue observed UV continuum slopes, which is made more complex due to
strong nebular continuum and line emission (Topping et al., 2022). To aid in
fitting these galaxies, we generated additional templates using Flexible
Stellar Population Synthesis (fsps, Conroy & Gunn, 2010), and added these to
the “5Myr” and “25Myr” simple stellar population models introduced in Coe et
al. (2006) for fitting blue galaxies in HUDF. We show our additional templates
in the right panel of Figure 1, and we provide these templates online hosted
on Zenodo: https://doi.org/10.5281/zenodo.7996500. Multiple templates from the
full set contain nebular continuum and line emission, including that from
Lyman-$\alpha$.

In each redshift bin considered, EAZY combines all of the available templates
together and applies an IGM absorption consistent with the redshift (Madau,
1995). The best fit in that redshift bin, measured using the minimum
$\chi^{2}$, is recorded in a $\chi^{2}(z)$ surface that is output from the
program. We explored the redshift range $z=0.01-22$, with a redshift step size
$\Delta z=0.01$. We did not adopt any apparent magnitude priors, as the exact
relationship between galaxy apparent magnitude and redshift at $z>8$ is
currently not well constrained, so any attempt to impose a prior would serve
to only remove faint objects from the sample. To prevent bright fluxes from
overly constraining the fits and to account for any photometric calibration
uncertainties not captured by the offset procedure described below (e.g. due
to detector specific offsets as observed in Bagley et al., 2023), we set an
error floor on the photometry of 5%, and additionally, we used the EAZY
template error file “template error.v2.0.zfourge” to account for any
uncertainties in the templates as a function of wavelength. We also explored
the use of the EAZY templates discussed in Larson et al. (2023), which were
used in finding high-redshift galaxies in the JWST Cosmic Evolution Early
Release Science (CEERS) observations, and we describe how using these
photometric redshifts affects our final sample in Section 4.8.

Figure 1: EAZY templates used in this work. In the left panel, we show the
EAZY “v1.3” templates, and in the right panel, the new EAZY templates created
for fitting to JADES galaxies. The templates are presented in $F_{\nu}$ units
normalized at ${2.8\mu}$m. These templates include both UV-faint quiescent and
UV-bright star-forming populations, and were both compiled from the literature
and created using Flexible Stellar Population Synthesis (fsps, Conroy & Gunn,
2010).

To match the EAZY template set to the observed fluxes in our catalog, we
estimated photometric offsets with EAZY. We calculated the offsets for GOODS-S
and GOODS-N data separately, where we first fit the observed photometry for a
sample of galaxies with an SNR in F200W between 5 and 20, and calculated the
offsets from the observed photometry to the template photometry. We then
applied these offsets to the photometry and re-fit, iterating on this
procedure. We list the final photometric offsets that we used for GOODS-S and
GOODS-N, normalized to F200W, in Table 2. These offsets are within 10% of
unity for all of the filters, with the exception of a large offset used for
the F850LP observations in GOODS-N. We find that the F850LP depths are among
the shallowest in our dataset (Table 1) which is likely contributing to the
large offset. While we observe differences between the GOODS-S and GOODS-N
offsets, this is primarily driven by the comparison of the HST/ACS photometry
to the NIRCam photometry. To demonstrate this, we recalculated the photometric
redshifts but used identical filter sets between the sources in the two fields
excluding the HST/ACS bands and the NIRCam medium bands F182M, F210M, F430M,
F460M, and F480M where we have limited coverage in these filters in GOODS-S
and GOODS-N. The median difference in the photometric offsets between the
GOODS-S and GOODS-N fits for the remaining filters as provided in Table 2 is
0.006 with a standard deviation of 0.012. However, when we calculate the
offsets without the HST/ACS bands or the NIRCam medium bands, the median
difference goes down to 0.001 and a standard deviation of only 0.004,
consistent with no difference.

Table 2: EAZY-derived photometric offsets, normalized to F200W.  |  | GOODS-S | GOODS-N
---|---|---|---
Instrument | Filter | Offset | Offset
HST | F435W | 1.021 | 1.072
HST | F606W | 1.002 | 0.976
HST | F775W | 1.009 | 0.996
HST | F814W | 0.962 | 0.998
HST | F850LP | 0.919 | 0.774
NIRCam | F070W | 0.981 | -
NIRCam | F090W | 0.987 | 1.012
NIRCam | F115W | 1.008 | 1.020
NIRCam | F150W | 0.994 | 0.989
NIRCam | F182M | 1.001 | 0.991
NIRCam | F200W | 1.000 | 1.000
NIRCam | F210M | 1.014 | 1.006
NIRCam | F277W | 0.998 | 0.990
NIRCam | F335M | 1.035 | 1.024
NIRCam | F356W | 1.057 | 1.047
NIRCam | F410M | 1.071 | 1.057
NIRCam | F430M | 1.014 | -
NIRCam | F444W | 1.015 | 1.009
NIRCam | F460M | 0.956 | -
NIRCam | F480M | 1.017 | -

We used the $\chi^{2}(z)$ values output from EAZY to calculate a probability
$P(z)$ assuming a uniform redshift prior: $P(z)=\exp{[-\chi^{2}(z)/2]}$, where
we normalize such that $\int P(z)dz=1.0$. The $P(z)$ and $\chi^{2}(z)$ values
allowed us to calculate $P(z>7)$, the summed probability from EAZY that the
galaxy is at $z>7$, as well as the $\chi^{2}$ minimum for EAZY fits restricted
to $z<7$. These statistics, and others, are helpful for identifying and
removing interlopers from our sample.

In Figure 2 we show the EAZY fit to an object in GOODS-S, JADES-
GS-53.17551-27.78064, along with the $P(z)$ surface, and the JADES NIRCam
thumbnails. The source is an F115W dropout, with no visible flux at shorter
wavelengths. The fit constrained at $z<7$ produces significantly more F115W
flux than is observed, lending evidence of this galaxy being at $z>9$.

Figure 2: Example best-fit SED for object JADES-GS-53.17551-27.78064, at the
best-fit redshift $z_{a}=9.66$. We plot the NIRCam photometry with red points,
and the HST photometry with light purple points. The error bars represent the
1$\sigma$ uncertainties on the fluxes. We plot $2\sigma$ upper limits with
downward pointing triangles. The blue line represents the fit corresponding to
$z_{a}$ and the gold line shows the best fit at $z<7$. We show the minimum
$\chi^{2}$ value for the $z_{a}$ fit, as well as the $\Delta\chi^{2}$ value
corresponding to the difference between the minimum $\chi^{2}$ and the
$\chi^{2}$ for the fit at $z<7$. In the inset, we plot $P(z)$, with the
1$\sigma$, 2$\sigma$, and 3$\sigma$ uncertainty regions derived from the
$P(z)$ surface with shades of grey, and $z_{a}$ with a blue line, along with
the $P(z)$ distribution for the $z<7$ best fit in gold (also normalized to 1).
Above the inset we provide the summed probability of the source being at
$z>7$, along with the EAZY redshifts corresponding to $\sigma_{68,low}$ and
$\sigma_{68,high}$. Below the SED we plot $2^{\prime\prime}\times
2^{\prime\prime}$ thumbnails for the JADES NIRCam filters.

###  3.2 High-Redshift Galaxy Selection and Catalogs

Because of the extensive deep photometric data for the GOODS-S and GOODS-N
fields, we chose to use the EAZY photometric redshifts for finding $z>8$
candidates, as template fitting utilizes more photometric data points in the
fit than color selection by itself. Following work done in the literature
(Finkelstein et al., 2023), we selected galaxies at $z>8$ by imposing these
rules on the EAZY fits:

  1. 1.

The redshift of the fit corresponding to the minimum $\chi^{2}$, $z_{a}$, must
be greater than 8.

  2. 2.

The SNR in at least two photometric bands must be above 5. For this study, we
chose NIRCam F115W, F150W, F200W, F277W, F335M, F356W, F410M, or F444W, as
these filters are longward of the Lyman-$\alpha$ break at $z>8$. We used the
photometry derived using $0.2^{\prime\prime}$ diameter apertures for measuring
this SNR.

  3. 3.

The summed probability of the galaxy being above $z>7$ must be greater than
70%, or ${\int_{7}^{22}P(z)dz>0.7}$.

  4. 4.

The difference between the overall minimum $\chi^{2}$ and the minimum
$\chi^{2}$ at $z<7$, $\Delta\chi^{2}$, must be greater than 4.

  5. 5.

There should be no object within $0.3^{\prime\prime}$ (10 pixels in the final
JADES mosaics), or within the object’s bounding box, that is 10 times brighter
that the object.

For this study, we targeted galaxies at $z_{a}>8$ as galaxies above this
redshift should have no observed flux in the JWST/NIRCam F090W filter. This
allows us to use the deep JADES F090W observations to aid in visually
rejecting lower-redshift contaminants. The second requirement, that the source
be detected in multiple bands, was chosen to ensure that the sources we
selected were not artifacts found in individual exposures such as cosmic rays
or bad pixels. We imposed the EAZY $\int_{7}^{22}P(z)>0.7$ (which we will
shorten to “$P(z>7)$”) and $\Delta\chi^{2}$ limits in order to help remove
objects where EAZY could fit the observed SED at low redshift with high
probability. In Harikane et al. (2023), the authors recommend the use of a
more strict cut, $\Delta\chi^{2}>9$, and we consider this cut in Section 5. We
also, in Section 4.4, discuss those objects where $\Delta\chi^{2}<4$ in our
sample, as these sources, though faint, may contain true high-redshift
galaxies that should be considered. Finally, we remove objects with close
proximity to bright sources because of the possibility of selecting tidal
features or stellar clusters near to the edges of relatively nearby galaxies.
We list those objects that satisfied our other requirements but were close to
a brighter source, along with discussion of these targets, in Section 4.5. We
chose not to implement a direct cut on $\chi^{2}$ as this metric is dependent
on the flux uncertainties, which vary across the field in such a way as to
make a comparison of the value between objects difficult and potentially non-
meaningful. We still report the resulting $\chi^{2}$ values, however. In
comparison, the $\Delta\chi^{2}$ value is calculated from two fits to the same
photometry and uncertainties, and is helpful in exploring the relative
goodness of fits at different redshifts.

These cuts resulted in 1078 objects in GOODS-S and 636 objects in GOODS-N.
From here, we began the process of visual inspection, first to remove obvious
non-astrophysical data artifacts, including extended diffraction spikes from
stars, and hot pixels caused by cosmic rays. We also removed extended,
resolved low-redshift, dusty sources, many of which were not visible in HST
imaging. These sources were identified by very red slopes between 1 and
5$\mu$m, and have half-light radii $r_{\mathrm{half}}\gtrsim 1^{\prime\prime}$
in the filters where they are observed. These sources comprise only $\sim
0.4$% of the objects that satisfy our cuts. After removing these sources, we
were left with 580 possible objects in GOODS-S, and 212 objects in GOODS-N.
There is a much larger fraction of spurious sources in GOODS-N as compared to
GOODS-S as these data had a larger number of bright pixels and cosmic rays,
which primarily affected the NIRCam long-wavelength channels.

After this initial inspection, authors KH, JH, DE, MWT, CNW, LW, and CS
independently graded each target with a grade of Accept, Reject, or Review.
For those objects where $50\%$ or more of the reviewers accepted the
candidate, it was then added to the final candidate list. In cases where
greater than $50\%$ of the reviewers chose to reject the candidate, this
candidate was removed entirely from the candidate list. In all other cases (57
objects in GOODS-N and 102 objects in GOODS-S), the reviewers did one more
round of visual inspection with only the grades Accept or Reject, with a
larger discussion occurring for objects where necessary. Again, a 50% of
Accept grades was required for these galaxies under review to be listed as
part of the final sample.

##  4 Results

Table 3: Overview of Columns in the $z>8$ Source Catalog

Column | Description
---|---
1 | JADES ID
2, 3 | Right ascension and declination, in decimal degrees, of the source
4 |  $m_{\mathrm{F277W,Kron}}$ (AB)
5 - 11 |  EAZY $z_{a}$, $\sigma_{68,low}$, $\sigma_{68,high}$, $\sigma_{95,low}$, $\sigma_{95,high}$, $\sigma_{99,low}$, $\sigma_{99,high}$
12 |  EAZY $\int_{7}^{22}P(z)dz$
13 |  EAZY minimum $\chi^{2}$
14 |  EAZY minimum $z_{a}$ $(z<7)$
15 |  EAZY $\chi^{2}$ $(z<7)$
16 |  EAZY $\Delta\chi^{2}$
17, 18 | Spectroscopic Redshift, Source (FRESCO or NIRSpec)
19 | $M_{UV}$
20 | Flag indicating the source is fit by a brown dwarf model within $\Delta\chi^{2}<4$
21 | Flag indicating whether or not the source is unresolved ($r_{\mathrm{eff,F444W}}<0.063^{\prime\prime}$)
22, 23 | HST/ACS F435W Flux, 1$\sigma$ uncertainty (nJy)
24, 25 | HST/ACS F606W Flux, 1$\sigma$ uncertainty (nJy)
26, 27 | HST/ACS F775W Flux, 1$\sigma$ uncertainty (nJy)
28, 29 | HST/ACS F814W Flux, 1$\sigma$ uncertainty (nJy)
30, 31 | HST/ACS F850LP Flux, 1$\sigma$ uncertainty (nJy)
32, 33 | JWST/NIRCam F070W Flux, 1$\sigma$ uncertainty (nJy)
34, 35 | JWST/NIRCam F090W Flux, 1$\sigma$ uncertainty (nJy)
36, 37 | JWST/NIRCam F115W Flux, 1$\sigma$ uncertainty (nJy)
38, 39 | JWST/NIRCam F150W Flux, 1$\sigma$ uncertainty (nJy)
40, 41 | JWST/NIRCam F182M Flux, 1$\sigma$ uncertainty (nJy)
42, 43 | JWST/NIRCam F200W Flux, 1$\sigma$ uncertainty (nJy)
44, 45 | JWST/NIRCam F210M Flux, 1$\sigma$ uncertainty (nJy)
46, 47 | JWST/NIRCam F277M Flux, 1$\sigma$ uncertainty (nJy)
48, 49 | JWST/NIRCam F335M Flux, 1$\sigma$ uncertainty (nJy)
50, 51 | JWST/NIRCam F356W Flux, 1$\sigma$ uncertainty (nJy)
52, 53 | JWST/NIRCam F410M Flux, 1$\sigma$ uncertainty (nJy)
54, 55 | JWST/NIRCam F430M Flux, 1$\sigma$ uncertainty (nJy)
56, 57 | JWST/NIRCam F444W Flux, 1$\sigma$ uncertainty (nJy)
58, 59 | JWST/NIRCam F460M Flux, 1$\sigma$ uncertainty (nJy)
60, 61 | JWST/NIRCam F480M Flux, 1$\sigma$ uncertainty (nJy)
62 | JADES Footprint Region

Note. — We provide these values for the primary $z>8$ sample with
$\Delta\chi^{2}>4$, as well as the subsamples outlined in the text:
$\Delta\chi^{2}<4$ and those proximate to brighter sources.

Our final $z>8$ samples consist of 535 objects in GOODS-S and 182 objects in
GOODS-N. In Table 3 we provide the descriptions of the columns in our final
catalog; the catalog itself is provided as an online table on Zenodo:
https://doi.org/10.5281/zenodo.7996500. We include $0.2^{\prime\prime}$
diameter aperture photometry in each of the observed photometric bands, as
well as the EAZY $z_{a}$, $\chi^{2}$, $P(z>7)$, and $\Delta\chi^{2}$ values
used in selecting the galaxies. We also provide the $\sigma_{68}$,
$\sigma_{95}$, and $\sigma_{99}$ confidence intervals estimated from the
$P(z)$ distribution. In this table we also list the $z>8$ candidates that have
EAZY $\Delta\chi^{2}<4$, and we will discuss these sources in Section 4.4.
Similarly, in our output table, we list those $z>8$ candidates that were
either within $0.3^{\prime\prime}$ or within the bounding box of a target 10
times brighter than the candidate, which we discuss in Section 4.5.

We show the positions of the GOODS-N sources in the left panel and the GOODS-S
sources in the right panel of Figure 3. On these figures, we include both
those with EAZY $\Delta\chi^{2}>4$ (dark points) and EAZY $\Delta\chi^{2}<4$
(lighter points). The relatively higher density of sources in the southern
portion of the GOODS-N observations compared to the northern portion is a
result of the increased observational depth in that region. In GOODS-N, we
find 2.1 objects in our $z>8$ sample per square arcminute in the NE footprint,
and 4.3 objects per square arcminute in the SW footprint. Similarly, the
deepest portions of the JADES GOODS-S coverage are the large rectangular JADES
Deep region, and the smaller 1210 parallels, where a significantly higher
density of objects are detected. In GOODS-S, we find 7.8 objects in our $z>8$
sample per square arcminute in JADES Deep, 4.5 objects per square arcminute in
JADES Medium, 4.1 objects per square arcminute in the 1286 parallel, and 13.9
objects per square arcminute in the 1210 parallel.

Figure 3: (Left) GOODS-N footprint showing the positions of the $z>8$
candidates. The southeastern portion (dashed) of the GOODS-N area is deeper
than the northwestern portion (solid), resulting in a larger density of
candidate high-redshift galaxies. In grey, we plot the outline of the Hubble
Deep Field (North) (Williams et al., 1996) as a comparison to the JADES survey
area. (Right) GOODS-S footprint. The dashed blue outline highlights the JADES
Deep GOODS-S area, and the solid blue outline highlights the JADES Medium
GOODS-S region. The colored squares denote additional NIRCam pointings from
the JEMS survey (burgundy), the 1210 parallels (purple), and the 1286
parallels (green). In grey, we plot the outline of the Hubble Ultra Deep Field
(Beckwith et al., 2006). There is a noticeable increase in the density of
sources in the JADES Deep and the ultra-deep 1210 parallel footprint.

In Figure 4, following similar work done in the literature (Finkelstein et
al., 2023; Pérez-González et al., 2023; Austin et al., 2023), we show the
F277W observed AB magnitude measured using a Kron aperture against the EAZY
photometric redshift for each candidate $z>8$ galaxy in GOODS-S and GOODS-N.
Across the top we show the distribution of the photometric redshifts, and on
the right side we show the F277W magnitude distribution for the photometric
redshift sample as well as the GOODS-N and GOODS-S sample independently. For
those objects where we have spectroscopic redshifts from either NIRSpec or
FRESCO, we plot this value instead of the photometric redshift, and indicate
those galaxies with larger points with black outlines. The GOODS-S sample, by
virtue of the deeper coverage, extends to much fainter F277W magnitudes. On
this diagram, the galaxy GN-z11 (Oesch et al., 2016; Bunker et al., 2023b;
Tacchella et al., 2023) is the brightest source, as one of two galaxies at
$m_{\mathrm{F277W,Kron}}<26$ (the other is JADES-GS-53.10394-27.89058, at
$z_{a}=8.35$). The redshifts seen in the main panel are discrete because of
how EAZY fits galaxies at specific redshift steps.

In Figure 4 we can see how the usage of wide filters for estimating
photometric redshift leads to relative dearths of objects at $z\sim 10$ and
$z\sim 13$, as these redshifts are where the Lyman-$\alpha$ break is between
the F090W, F115W, and F150W filters. This is an artificial effect - for
Lyman-$\alpha$-break galaxies, estimations of precise redshifts are highly
predicated on the flux in the band that probes the break, and when the break
sits between filters, the resulting redshifts are more uncertain. For example,
faint galaxies at $z\sim 9-11$ can have similar SEDs where there is flux
measured in the F150W filter and none measured in the F115W filter. This
degeneracy results in photometric redshifts of these galaxies of $z_{a}\sim
9.5$, with broad $\chi^{2}$ minima reflecting larger redshift uncertainties.
At slightly higher redshifts, however, the Lyman-$\alpha$ break moves into the
F150W filter and this results in red F150W - F200W colors, leading to more
precise photometric redshifts. This same effect is seen between the F150W and
F200W filters at $z\sim 13$. The usage of medium-band filters, like NIRCam
F140M, F162M, F182M, and F210M would help mitigate this effect somewhat for
galaxies at these redshifts. We further explore these gaps by simulating
galaxies across a uniform redshift range in Appendix A.

Figure 4: F277W AB Kron Magnitude plotted against the best-fitting EAZY
$z_{a}$ photometric redshift for the 717 galaxies and candidate galaxies in
the GOODS-S (blue) and GOODS-N (red) $z>8$ samples. Along the top we show the
redshift distribution for the full sample (grey) as well as the GOODS-S and
GOODS-N samples. On the right we show the magnitude distribution in a similar
manner. The points colored with dark circles are plotted with the available
spectroscopic redshifts for those sources, which, in many cases, extends to
$z<8$. We discuss these sources in Figure 4.9. There is a lack of sources at
$z\sim 10$ because of how the Lyman-$\alpha$ break falls between the NIRCam
F115W and F150W at this redshift, making exact photometric redshift estimates
difficult. The brightest source in the sample is the spectroscopically-
confirmed galaxy GN-z11 at $z_{spec}=10.6$, and the highest-redshift
spectroscopically-confirmed source is JADES-GS-z13-0 at $z_{spec}=13.2$. There
is one source JADES-GN-189.15981+62.28898, at $z_{a}=18.79$, which we plot as
a right-facing arrow in the plot and discuss in Section 4.3.

In this section we discuss the candidates in three subcategories: $z_{a}=8-10$
(Section 4.1), $z_{a}=10-12$ (Section 4.2), and $z_{a}>12$ (Section 4.3). For
each subcategory we describe the properties of the sample, plot example SEDs
for galaxies spanning the magnitude and redshift range, and discuss notable
examples.

###  4.1 $z_{phot}=8-10$ Candidates

Example $z=8-10$ Candidates

Figure 5:  Example SEDs for eight $\Delta\chi^{2}>4$ candidate GOODS-S and
GOODS-N galaxies at $z_{a}=8-10$. In each panel, the colors, lines, and
symbols are as in Figure 2.

We find 547 total galaxies and galaxy candidates combined across the JADES
GOODS-S (420 sources) and GOODS-N (127 sources) areas at $z_{a}=8-10$. We show
a subsample of the EAZY SED fits and the JADES thumbnails for eight example
candidate high-redshift galaxies in this photometric redshift range in Figure
5. In each plot, we show both the minimum $\chi^{2}$ fit, as well as the fit
constrained to be at $z<7$. We chose these objects from the full sample to
span a range of F277W Kron magnitudes as well as photometric redshifts.

Because of the availability of both NIRSpec and FRESCO spectroscopy for our
sample, there are 34 (27 in GOODS-S and 7 in GOODS-N) galaxies in this
photometric redshift range where a spectroscopic redshift has been measured.
For 14 of these sources (13 in GOODS-S and 1 in GOODS-N), the resulting
spectroscopic redshift $z_{spec}=7.65-8.0$. Because these objects satisfied
our photometric redshift selection criteria, we choose to include them in our
sample, and discuss their spectroscopic redshifts in Section 4.9.

There are a number of sources in this photometric redshift range with extended
morphologies, often seen in the JADES data as multiple clumps observed in the
images at shorter wavelengths. In Figure 6, we show a subsample of nine
resolved galaxies with $z_{a}=8-9$. For each object we show the F090W, F115W,
and F356W thumbnails, along with a color image combining these three filters.
Each thumbnail is $2^{\prime\prime}$ on a side, showcasing the resolved sizes
of some of these targets. At $z=8-10$, $1^{\prime\prime}$ corresponds to
$4.6-4.9$ kpc, and we provide a scale bar of $0.5^{\prime\prime}$ in each
panel. At these redshifts, F090W is to the blue of the Lyman-$\alpha$ break,
so the galaxies should not appear in this filter, F200W spans the rest-frame
UV and F356W spans the rest-frame optical continuum. We are then seeing UV-
bright star-forming clumps in the F200W filter, and rest-frame $\sim 4000$Å
stellar continuum in F356W. We show two sources, JADES-GS-53.1571-27.83708
(top row, left column), and JADES-GS-53.08738-27.86033 (top row, middle
column), which have spectroscopic redshifts from FRESCO at $z_{spec}=7.67$ and
$z_{spec}=7.96$ respetively, as indicated below the photometric redshifts in
the color panel.

These nine sources show multiple irregular morphologies, and many are
elongated. JADES-GN-189.18051+62.18047 is an especially complex system at
$z_{a}=8.92$ with four or five clumps that span almost 7 kpc at this
photometric redshift, similar to the “chain of five” F150W dropout system
presented in Yan et al. (2023). Five of the extended sources we highlight were
previously presented in the literature: JADES-GS-53.1571-27.83708, JADES-
GS-53.08738-27.86033, JADES-GS-53.08174-27.89883, JADES-GS-53.1459-27.82279
and JADES-GS-53.10393-27.89059 (McLure et al., 2013; Bouwens et al., 2015;
Finkelstein et al., 2015; Harikane et al., 2016; Bouwens et al., 2021). Given
the depth and resolution of NIRCam, we can see new details for these sources
from what was observed in the HST ACS and WFC3 observations, such as the
nearly $\sim 0.8^{\prime\prime}$-long haze to the northeast for JADES-
GS-53.10393-27.89059, which corresponds to about 4 kpc at the candidate
photometric redshift.

Example $z=8-9$ Resolved Candidates

Figure 6:  Color thumbnails for a selection of nine $z_{a}=8-9$ resolved
galaxies with multiple components. Each thumbnail is $2^{\prime\prime}$ on a
side, and we include a size bar showing $0.5^{\prime\prime}$ for each object.
The color image is composed of F356W, F200W, and F090W as red, green, and blue
respectively. We also show images in those filters for each object separately
to demonstrate the dropout nature of these objects in the F090W filter.

###  4.2 $z_{phot}=10-12$ Candidates

Example $z=10-12$ Candidates

Figure 7:  Example SEDs for eight $\Delta\chi^{2}>4$ candidate GOODS-S and
GOODS-N galaxies at $z_{a}=10-12$. In each panel, the colors, lines, and
symbols are as in Figure 2.

We find a total of 137 galaxies and candidate galaxies at at $z_{phot}=10-12$:
92 in GOODS-S and 45 in GOODS-N. We show the EAZY SED fits and the JADES
thumbnails for eight example candidates in this photometric redshift range in
Figure 7.

In the GOODS-S region, this redshift range includes two of the
spectroscopically-confirmed galaxies from Robertson et al. (2023) and Curtis-
Lake et al. (2023), JADES-GS-z10-0 ($z_{spec}=10.38^{+0.07}_{-0.06}$) and
JADES-GS-z11-0 ($z_{spec}=11.58^{+0.05}_{-0.05}$). The EAZY photometric
redshifts for these targets are $z_{a}=10.84$ for JADES-GS-z10-0, and
$z_{a}=12.31$ for JADES-GS-z11-0. Both photometric redshifts are higher than
the measured spectroscopic redshift, but considering the $P(z)$ uncertainty in
both measurements, the measurements are within $2\sigma$ of the true values.
Indeed, the $\Delta\chi^{2}$ between the minimum value corresponding to
$z_{a}$ and the value at $z_{spec}$ is 10.25 for JADES-GS-z10-0 and 1.75 for
JADES-GS-z11-0. In Robertson et al. (2023), the authors estimate photometric
redshifts for these sources using the Bayesian stellar population synthesis
fitting code _Prospector_ (Johnson et al., 2021) and recover $P(z)$ surfaces
that are similarly offset to higher values than the spectroscopic redshifts.
In the GOODS-N region, we find the brightest object overall in our sample (a
Kron F277W aperture magnitude of 25.73 AB), GN-z11, discussed at length in
Tacchella et al. (2023) and spectroscopically confirmed to lie at $z=10.603\pm
0.001$ in Bunker et al. (2023b). In our EAZY fit, we estimate $z_{a}=11.0$,
which is within 2$\sigma$ of the spectroscopic redshift, but again, higher
than the spectroscopic redshift. We further explore this difference in Section
4.9.

In Tacchella et al. (2023), the authors identify nine galaxies within 10
comoving Mpc ($212^{\prime\prime}$) of GN-z11 that have photometric redshifts
between $z_{a}=10-11$. Six of these sources are included in our
$\Delta\chi^{2}>4$ sample (JADES-GN+189.1162+62.22007, JADES-
GN+189.07603+62.2207, JADES-GN+189.12549+62.2382, JADES-GN+189.08667+62.2395,
JADES-GN+189.05971+62.2457, and JADES-GN+189.05166+62.2507, given as 465, 544,
4418, 4811, 6862, and 8597 in Tacchella et al., 2023), while the other three
sources (JADES-GN-189.07355+62.2375, JADES-GN-189.19975+62.2703, and JADES-
GN-189.05413+62.2179 given as 4155, 13543 and 62240 in Tacchella et al., 2023)
are not in our final sample as these sources did not satisfy the requirement
of having a flux SNR $>5$ in at least two bands to the red of the potential
Lyman-$\alpha$ break, or in the case of JADES-GN-189.07355+62.2375, this
source has $z_{a}<8$ with the updated photometry in this study.

We want to highlight three galaxies seen in Figure 7 because of their
extended, somewhat complex morphologies. JADES-GS-53.13918-27.84849
($z_{a}=10.45$, first row, right column), an F115W dropout, has three
components and spans $0.5^{\prime\prime}$, which is 2 kpc at this photometric
redshift. We observe an increase in the F444W flux over what is seen at 3 -
4$\mu$m, which could either be a result of [OII]$\lambda$3727 emission at this
redshift or evidence of a Balmer break. The F115W dropout JADES-
GS-53.09872-27.8602 ($z_{a}=10.69$, second row, right column) is the southern
clump of two morphologically distinct components separated by
$0.3^{\prime\prime}$ (1.2 kpc at this photometric redshift) in the rest-frame
UV, which becomes less distinct at longer wavelengths. The northern clump,
JADES-GS-53.09871-27.86016 ($z_{a}=9.59$), is also in our sample, but the EAZY
fit prefers a lower photometric redshift which is consistent to within
$1\sigma$. Finally, JADES-GS-53.07597-27.80654 ($z_{a}=11.27$, third row,
right column) consists of two, bright, connected clumps separated by
$0.2^{\prime\prime}$ (580 pc at this photometric redshift). The sources are
detected as separate clumps in the relatively shallower FRESCO F182M and F210M
data as well. These sources could be interacting seed galaxies or star-forming
clumps in the very early universe.

###  4.3 $z_{phot}>12$ Candidates

We find 33 galaxies and candidate galaxies across both the JADES GOODS-S (23
sources) and GOODS-N (10 sources) footprints at $z>12$. We show their SEDs and
thumbnails for eight examples in Figure 8, and we show the remaining in
Figures 18, 19, and 20 in Appendix B. For objects at these redshifts, the
Lyman-$\alpha$ break falls in the F150W filter at $z=12$, in between the F150W
and F200W filters at $z=13.2$, and in between the F200W and F277W filters at
$z=17.7$. The objects in our $z>12$ sample, then, are a mixture of solid F150W
dropouts and more tentative galaxies that show evidence for faint F200W flux
associated with the Lyman-$\alpha$ break lying in that filter.

Our sample in this redshift range includes the other two high-redshift
spectroscopically-confirmed galaxies from Robertson et al. (2023) and Curtis-
Lake et al. (2023), JADES-GS-z12-0 ($z_{spec}=12.63^{+0.24}_{-0.08}$) and
JADES-GS-z13-0 ($z_{spec}=13.20^{+0.04}_{-0.07}$). We estimate EAZY
photometric redshifts for these targets of $z_{a}=12.46$ for JADES-GS-z12-0,
and $z_{a}=13.41$ for JADES-GS-z13-0. While both photometric redshifts are
quite uncertain due to the width of the bands used to probe the Lyman-$\alpha$
break, the range of uncertainties based on the EAZY $\sigma_{68}$ redshifts
are consistent with the spectroscopic redshifts.

Because of the importance of these galaxies towards understanding galaxy
formation in the very early universe, we will discuss the candidate galaxies
in this redshift range individually, in order of decreasing photometric
redshift. In our descriptions. We include brief discussions of two of the
spectroscopically confirmed galaxies from Robertson et al. (2023) and Curtis-
Lake et al. (2023), JADES-GS-z12-0 and JADES-GS-z13-0, but we refer the reader
to these papers for more detailed discussions of these sources.

$z>12$ Candidates, Part I

Figure 8:  Example SEDs for eight candidate GOODS-S and GOODS-N galaxies at
$z_{a}>12$. The remainder of the objects are in Figures 18, 19, and 20 in
Appendix B. In each panel, the colors, lines, and symbols are as in Figure 2.

JADES-GN-189.15981+62.28898 ($z_{a}=18.79$) This F200W dropout, the highest-
redshift candidate in our sample, is clearly detected in multiple LW filters.
There is no detection in the F200W filter, and we calculate a dropout color
assuming a 2$\sigma$ upper-limit on the F200W flux of
$m_{F200W}-m_{F277W}>1.29$. While this source lies in the relatively shallower
GOODS-N NW portion of the survey, the large $\Delta\chi^{2}$ provides strong
evidence for this source being at high redshift.

JADES-GS-53.12692-27.79102 ($z_{a}=15.77$) This is one of the more intriguing
objects in our sample, as it is a relatively bright ($m_{F277W,Kron}=29.37$)
F150W dropout detected at greater than $16\sigma$ in all of the detection
bands. While there may be F115W flux observed in the thumbnail, it is only at
SNR = 1.76. Caution should be exercised in adopting the derived redshift for
this source as a result, since this object’s fluxes are consistent with it
being at $z=5$.

JADES-GS-53.0541-27.70399 ($z_{a}=15.67$) This F150W dropout has quite large
photometric redshift uncertainties, but the $\sigma_{68}$ range is still
consistent with it being at $z>12$. The source $1^{\prime\prime}$ to the east
is a potential F090W dropout with $z_{a}=8.24$, but we measure $P(z<7)=0.68$
from the EAZY fit, so it does not appear in our sample.

JADES-GS-53.19592-27.7555 ($z_{a}=15.32$) This slightly extended F150W dropout
has SNR $>5$ in three filters: F277W, F356W, and F444W. It is also over
$3^{\prime\prime}$ away from any bright sources. Because of the non-detection
in F150W, we estimate that $m_{F150W}-m_{F200W}>0.74$ given a 2$\sigma$ upper
limit on the observed F150W flux.

JADES-GS-53.07557-27.87268 ($z_{a}=15.31$) This is one of the faintest $z>12$
sources ($m_{F277W,Kron}=30.04$), although it is observed at SNR $>5$ in three
filters: F277W, F356W, and F444W. In the thumbnail we show how this candidate
is surrounded by other, brighter sources. The sources to the northwest and
southeast are both at $z_{a}\sim 1.0$, while the source with multiple
components to the northeast is an F435W dropout at $z_{a}=3.74$.

JADES-GS-53.17847-27.75591 ($z_{a}=15.13$) This very compact F150W dropout is
quite faint ($m_{F277W,Kron}=29.79$), and is relatively isolated, with the
nearest bright galaxy being almost $2^{\prime\prime}$ to the west. The lack of
significant detections in the bands to the blue of the proposed Lyman-$\alpha$
break ($m_{F150W}-m_{F200W}>1.14$) provides strong evidence of this source’s
photometric redshift.

JADES-GS-53.12914-27.86075 ($z_{a}=15.07$) This F150W dropout is strongly
detected (SNR $>7$) in F200W and F277W, with $m_{F150W}-m_{F200W}=1.73$. It is
detected at SNR $>3$ in F210M, but not in F182M.

JADES-GN-189.32608+62.15725 ($z_{a}=14.77$) This is an F150W dropout
$0.5^{\prime\prime}$ northeast of an F850LP dropout galaxy at $z_{a}=5.2$,
which is a slightly higher redshift than the potential secondary minimum in
the $P(z)$ surface for this source. We measure $m_{F150W}-m_{F200W}=2.46$, and
find that this source is still at $z>12$ within the $\sigma_{68}$ range on the
photometric redshift.

JADES-GS-53.02212-27.85724 ($z_{a}=14.59$) This slightly diffuse F150W dropout
has SNR $>5$ in all of the bands where it is detected, and we measure
$m_{F150W}-m_{F200W}=2.91$. It is near the western edge of the JADES medium
mosaic, and is $2.5^{\prime\prime}$ southeast of the star GOODS
J033205.16-275124.2.

JADES-GN-189.23606+62.16313 ($z_{a}=14.47$) This F150W dropout is faint
($m_{F277W,Kron}=29.40$), but has a $7\sigma$ detection in F277W, and a
$6\sigma$ detection with F356W. We measure a very red dropout color
$m_{F150W}-m_{F200W}=4.28$.

JADES-GS-53.10763-27.86014 ($z_{a}=14.44$) This is a faint, diffuse F150W
dropout that is within $1.5^{\prime\prime}$ of a larger galaxy at $z_{a}=0.9$.
While there is evidence of F115W flux in the thumbnail, it is only at a SNR =
1.64.

JADES-GS-53.07427-27.88592 ($z_{a}=14.36$) This F150W dropout is not detected
at SNR $<0.8$ in each of the bands shortward of the potential Lyman-$\alpha$
break, and we measure $m_{F150W}-m_{F200W}=4.05$. It is $1^{\prime\prime}$
away from a F435W dropout at $z_{a}=4.31$, and could be associated with that
source, as the secondary $P(z)$ peak indicates.

JADES-GN-189.16733+62.31026 ($z_{a}=14.33$) This F150W dropout is very bright
in F277W ($m_{F277W,Kron}=27.28$), pushing it above the distribution at these
redshifts as seen in Figure 4. It is within $0.5^{\prime\prime}$ of an F435W
dropout at $z_{a}=4.34$. As a result, the potential Lyman-$\alpha$ break for
this object could be a Balmer break if these two sources are associated at
similar redshifts.

JADES-GS-53.11127-27.8978 ($z_{a}=14.22$) This source is an F150W dropout
solid SNR $>5$ detections in the LW JADES filters. The SW fluxes for this
objects may be impacted by detector artifacts which are seen to the northwest
and southeast of the source.

JADES-GN-189.24454+62.23731 ($z_{a}=14.0$) This F150W dropout is only detected
with $>5\sigma$ in F277W (SNR = 7.32) and F356W (SNR = 7.08), and we measure
$m_{F150W}-m_{F200W}>0.93$.

JADES-GS-53.06475-27.89024 ($z_{a}=14.0$) This F150W dropout
($m_{F150W}-m_{F200W}>2.27$) is detected in the F277W filter at 19.9$\sigma$,
is found in the exceptionally deep GOODS-S JADES 1210 Parallel. In this
region, there are no medium band observations from either JEMS or FRESCO for
this source, and we do not see any detection in any of the WFC3 or ACS bands.
This source a quite promising high-redshift candidate, with a
$\Delta\chi^{2}\sim 65$.

JADES-GS-53.14673-27.77901 ($z_{a}=13.68$) This F150W dropout is quite well
detected in multiple bands, including F182M, but it has a fairly broad P(z)
surface, although the $\sigma_{68}$ values are consistent with $z>12$
solutions. At $z_{phot}\sim 13-14$, the fits are more unconstrained due to the
widths of the F150W and F200W photometric bands and the gap between them.

JADES-GS-53.14988-27.7765, ($z_{a}=13.41$) This source, also known as JADES-
GS-z13-0, was spectroscopically confirmed to be at $z_{\mathrm{spec}}=13.20$
in Curtis-Lake et al. (2023), and the NIRCam photometry and morphology for the
source was discussed in Robertson et al. (2023). The source is fairly bright
($m_{F200W,Kron}=28.81$) with a strong observed Lyman-$\alpha$ break, and the
$\sigma$68 range on the photometric redshift ($z_{\sigma 68}=12.92-14.06$) is
in agreement with the observed spectroscopic redshift.

JADES-GN-189.27873+62.2112 ($z_{a}=13.12$) This source has F182M and F210M
fluxes boosted by flux from a diffraction spike. This source has an F150W
detection at $2.4\sigma$, potentially demonstrating that it is at a slightly
lower redshift, as indicated by the large $P(z)$ distribution.

JADES-GN-189.11004+62.23638 ($z_{a}=13.12$) The F182M and F210M fluxes for
this F150W dropout ($m_{F150W}-m_{F200W}=2.69$) are also boosted by a
diffraction spike from a nearby star. There appears to be F115W flux at
$2.14\sigma$, but this is shifted to the northeast of the primary source by
$0.3^{\prime\prime}$ seen in F200W and F277W.

JADES-GS-53.06928-27.71539 ($z_{a}=12.69$) This is a faint
($m_{F277W,Kron}=29.73$) F150W dropout with a very red dropout color
$m_{F150W}-m_{F200W}=4.97$.

JADES-GN-189.33638+62.16733 ($z_{a}=12.53$) While this F150W dropout is faint
($m_{F277W,Kron}=30.01$), the fit indicates a blue UV slope and the object is
detected in multiple filters at $>5\sigma$, with $\Delta\chi^{2}=12.94$.

JADES-GS-53.18129-27.81043 ($z_{a}=12.52$) This very faint
($m_{F277W,Kron}=30.11$) F150W dropout has solid 8$\sigma$ detections in F200W
and F277W, and can be seen in the F356W thumbnail at 4$\sigma$.

JADES-GS-53.08468-27.86666 ($z_{a}=12.48$) This F150W dropout
($m_{F150W}-m_{F200W}=1.96$) has a slightly redder potential UV slope, and
this may be a low-redshift dusty interloper.

JADES-GS-53.16635-27.82156 ($z_{a}=12.46$) This galaxy, also known as JADES-
GS-z12-0, was originally spectroscopically confirmed to lie at
$z_{\mathrm{spec}}=12.63$ in Curtis-Lake et al. (2023), and the NIRCam
photometry and morphology for the source was discussed in Robertson et al.
(2023). Recent, deeper NIRSpec observations for this source showed C
III]$\lambda\lambda$1907,1909 line emission, indicating a spectroscopic
redshift of $z_{\mathrm{spec}}=12.479$ (D’Eugenio et al., 2023). This source
is a bright ($m_{F277W,Kron}=28.64$) F150W dropout
($m_{F150W}-m_{F200W}=2.01$) with a 26$\sigma$ detection in F277W, and is
observed at the $4-6\sigma$ level in the relatively shallow F182M and F210M
filters.

JADES-GS-53.02868-27.89301 ($z_{a}=12.39$) This source is an F150W dropout
with strong detections (SNR $>5$) in each filter to the red of the potential
Lyman-$\alpha$ break.

JADES-GS-53.10469-27.86187 ($z_{a}=12.27$) This source is an F150W dropout
with strong detections in F200W and F277W. The fluxes at F115W and F150W are
observed at 1.55$\sigma$ and 1.39$\sigma$ significance, respectively.

JADES-GN-189.27641+62.20724 ($z_{a}=12.19$) This source is well detected in
F200W and F277W (SNR $>10$ in both filters), but is quite faint at longer
wavelengths. There is a source $1.5^{\prime\prime}$ the southeast of the
target at $z_{spec}=2.44$ (Reddy et al., 2006), so we caution that the
observed Lyman-$\alpha$ break for the high-redshift candidate may be a Balmer
break at 1.5$\mu$m.

JADES-GN-189.09217+62.25544 ($z_{a}=12.16$) This is a bright
($m_{F277W,Kron}=28.53$) F150W dropout. The F150W detection is at a SNR
$=2.03$, while the F115W flux is only measured at the 1.55$\sigma$ level.

JADES-GS-53.19051-27.74982 ($z_{a}=12.08$) This is a bright
($m_{F277W,Kron}=28.72$) F115W dropout with multiple filters with $>10\sigma$
detections.

JADES-GS-53.14283-27.80804 ($z_{a}=12.06$) This object is an F150W dropout
that is primarily seen in F200W (SNR = 5.89) and F277W (SNR = 6.72). The fit
very strongly favors the high-redshift solution, and it does not seem be
associated with the nearby galaxy to the east, an F814W dropout at
$z_{a}=5.98$ with [OIII]$\lambda$5007 potentially boosting the F335M flux.

JADES-GS-53.18936-27.76741 ($z_{a}=12.05$) This source is a very faint,
slightly diffuse F150W dropout. While the $\Delta\chi^{2}$ is still in favor
of the $z>8$ fit, the lower-redshift solution would help explain the boosted
F210M flux as potentially arising from an [OIII] emission line, although the
F210M flux is only significant at 2.6$\sigma$.

We caution that photometric redshifts at $z>12$ are quite uncertain, and that
our sources are observed down to very faint magnitudes, and thus require deep
spectroscopic follow-up to confirm. In many cases we also raise the
possibility that the source is potentially associated with a nearby galaxy at
lower redshift. For the GOODS-S sources, continued observations extending both
the size of the JADES Medium region and the depth of JADES Deep planned for
Cycle 2 as part of JADES will help to provide evidence as to whether these
sources are truly at high-redshift or not.

###  4.4 $z>8$ Candidates with $\Delta\chi^{2}<4$

In the previous sections we explored those objects for which the EAZY fit
strongly favors a high-redshift solution. The fits to these sources at their
proposed photometric redshifts indicate strong Lyman-$\alpha$ breaks and more
robust upper limits on the photometric fluxes blueward of the break. For cases
where the observed HST/ACS or short-wavelength JWST/NIRCam fluxes have higher
uncertainties (for fainter objects or those objects in shallower parts of the
GOODS-S or GOODS-N footprint), fits at $z<7$ are less strongly disfavored,
leading to values of $\Delta\chi^{2}<4$.

We selected candidate $z>8$ galaxies in our sample that satisfy our criteria
outlined in Section 3.2, but where $\Delta\chi^{2}<4$. While the bulk of the
output EAZY $P(z)$ indicates that the galaxy is at high-redshift
($P(z>7)>0.7$), the minimum $\chi^{2}$ for the $z<7$ solution is more similar
to the overall minimum $\chi^{2}$ at $z>8$. In this section we explore these
targets, as they represent a non-insignificant number of candidates.

Following the initial selection of these objects, they were visually inspected
following the same routine as for the $\Delta\chi^{2}>4$ objects, where an
object was removed from the sample if the majority of reviewers flagged it for
rejection. Our final sample consists of 163 candidates in GOODS-S and 64
candidates in GOODS-N, for a total of 227 objects. These objects are also
plotted with lighter symbols in Figure 3. While these sources span the full
redshift range of the $\Delta\chi^{2}>4$ sample, the median F277W Kron
magnitude is 29.47 for the GOODS-S objects and 29.11 for the GOODS-N objects,
fainter than the median F277W magnitudes of the $\Delta\chi^{2}>4$ sources
(29.25 for GOODS-S and 28.62 for GOODS-N). This is expected as
$\Delta\chi^{2}$ is strongly dependent on the observed flux uncertainties for
each source.

Example $\Delta\chi^{2}<4$ Candidates

Figure 9:  Example SEDs for eight $\Delta\chi^{2}<4$ candidate GOODS-S and
GOODS-N galaxies. In each panel, the colors, lines, and symbols are as in
Figure 2.

In Figure 9 we highlight some targets from both GOODS-S and GOODS-N with
$\Delta\chi^{2}<4$, demonstrating the variety of targets in this subcategory.
The median F090W flux (measured in a $0.2^{\prime\prime}$ diameter aperture)
for the full sample of GOODS-S and GOODS-N $z>8$ candidates is -0.02 nJy (the
distribution is consistent with 0 nJy), while the median F090W flux for the
combined sample of $\Delta\chi^{2}<4$ targets is 0.39 nJy. Targets like JADES-
GS-53.04744-27.87208 ($z_{a}=12.33$) and JADES-GN-189.33478+62.1919
($z_{a}=12.38$) have faint F115W and F150W flux measurements (with high
uncertainties) consistent with dusty $z\sim 4$ solutions with strong emission
lines, similar to CEERS-93316 observed in Arrabal Haro et al. (2023a). Many of
these objects are also limited by the lack of deep HST/ACS data; JADES-
GS-53.04744-27.87208 only has coverage with F435W and F606W due to its
position in the southwest of the JADES GOODS-S footprint.

We include these sources and their fluxes to aid in the selection of high-
redshift galaxies in future deep JWST surveys with different filter selection
and observational depths. While a larger number of these objects may be lower
redshift interlopers masquerading as $z>8$ galaxies, this sample may serve as
a pool of additional sources to be placed on multi-object slit-masks in
follow-up spectroscopic campaigns to confirm source redshifts. In addition,
these objects are helpful with calibrating template sets as they have colors
that can be fit with models at low and high redshift.

###  4.5 $z>8$ Candidates Proximate to Brighter Sources

In addition to exploring the sources with $\Delta\chi^{2}<4$, we also looked
at objects (at all $\Delta\chi^{2}$ values) that were near bright sources,
being within $0.3^{\prime\prime}$ or the bounding box of a source with ten
times greater brightness. There is an increased probability that proximate
sources are at similar redshifts, and so we can compare the $\chi^{2}$
distribution of the brighter galaxy to that of the fainter high-redshift
candidate. At faint magnitudes, Balmer breaks and strong line emission can be
lead to sources being mistaken for higher redshift objects, which be be seen
by looking at the $\chi^{2}$ minima for these sources. In addition, being so
close to a bright source can potentially introduce flux into the circular
aperture photometry and change the observed colors of the candidate galaxy and
the shape of the SED. We went through the same visual classification procedure
for these sources as we did for the full sample, and ended up with 41
candidates (30 have $\Delta\chi^{2}>4$) in GOODS-S and 17 candidates (14 have
$\Delta\chi^{2}>4$) in GOODS-N. These sources have a median F277W Kron
magnitude of $m_{AB}=28.61$ for those in GOODS-S, and $m_{AB}=27.50$ for those
in GOODS-N, and range in redshift between $z=8.0-16.7$.

We want to specifically highlight some of the higher-redshift candidates from
this subsample. Notably, there are three galaxies at $z_{a}>12$: JADES-
GS-53.08016-27.87131 ($z_{a}=16.74$), JADES-GS-53.09671-27.86848
($z_{a}=12.03$), and JADES-GN-189.23121+62.1538 ($z_{a}=12.16$). JADES-
GS-53.08016-27.87131 has $\Delta\chi^{2}<4$, although this source is the most
interesting due to its photometric redshift. This source has a very faint
F200W detection ($\mathrm{SNR}>4$ in an $0.2^{\prime\prime}$ diameter
aperture), but is relatively bright at longer wavelengths (with an F277W AB
magnitude of 29.20). This source lies $3^{\prime\prime}-4^{\prime\prime}$
north of a pair of interacting galaxies at $z_{spec}=1.1$ (Bonzini et al.,
2012; Momcheva et al., 2016), and flux from the outskirts of these galaxies
may be contributing to the aperture photometry for this object, leading to an
artificially red UV slope. We caution that this source may be a stellar
cluster associated with this pair or the dusty galaxies that are to the north
of its position.

There are five objects in this subsample that have spectroscopic redshifts
from FRESCO: JADES-GS-53.12001-27.85645 ($z_{a}=8.33$, $z_{spec}=7.652$),
JADES-GS-53.13341-27.83909 ($z_{a}=8.18$, $z_{spec}=8.217$), JADES-
GS-53.07688-27.86967 ($z_{a}=8.57$, $z_{spec}=8.270$), JADES-
GS-53.10107-27.86511 ($z_{a}=8.49$, $z_{spec}=8.195$), and JADES-
GN-189.27457+62.21053 ($z_{a}=8.03$, $z_{spec}=8.015$). These sources have
[OIII]$\lambda$5007 line detections from FRESCO, demonstrating that while this
class of sources may be associated with their nearby brighter neighbors, there
are possible high-redshift galaxies among them.

###  4.6 Stellar Contamination

One primary source of contamination for high-redshift galaxy samples are low-
mass Milky Way stars and brown dwarfs which at low temperatures can have near-
IR colors similar to high-redshift galaxies, and many studies have explored
the selection of these sources from within extragalactic surveys (Ryan et al.,
2005; Caballero et al., 2008; Wilkins et al., 2014; Finkelstein et al., 2015;
Ryan & Reid, 2016; Hainline et al., 2020). Candidate brown dwarfs have been
observed in extragalactic surveys, such as GLASS (Nonino et al., 2023). To
explore whether our sample contains objects with a high probability of being a
possible brown dwarf, we looked at the sizes of the targets in our sample and
their fits to stellar models and observed brown dwarf SEDs.

We fit the targets in our sample using the jades-pipeline profile fitting
software, which utilizes the python lenstronomy package (Birrer & Amara, 2018;
Birrer et al., 2021). We fit each source, as well as the other nearby sources
within $2^{\prime\prime}$ and up to two magnitudes fainter than the primary
galaxy as Sersic profile. Objects that are fainter or farther from the source
are masked instead of fit. We use the final residuals to determine the
goodness of fit for each source. We measured the sizes using the NIRCam F444W
mosaic, as brown dwarfs are bright and unresolved at 4 $\mu$m (Meisner et al.,
2020). To determine whether an object was unresolved, we looked at those where
the observed half-light radius for each source was smaller than the NIRCam
long-wavelength channel pixels size ($0.063^{\prime\prime}$). We note that the
maximum half-light radius measured using the same procedure on a sample of
stars and brown dwarfs in GOODS-S and GOODS-N was $0.02^{\prime\prime}$, but
adopted a larger limit to broaden our search. These sources were identified
using both photometric fits to theoretical brown-dwarf models and
identification of sources with proper motions compared to HST observations,
and will be described further in Hainline et al. (in prep).

We fit the NIRCam photometry of our $z>8$ candidates using both the SONORA
cloud-free brown dwarf models from Marley et al. (2018) as well as a sample of
observed brown-dwarf observations from the SpeX Prism Spectral
Library111Compiled by Adam Burgasser and found online at
http://pono.ucsd.edu/~adam/browndwarfs/spexprism/.. As the SpeX spectra, in
general, are only observed to 2.5$\mu$m, we took a group of objects across the
temperature range that were detected in the Wide Field Infrared Survey
Explorer (WISE) allWISE catalog (Cutri et al., 2021) and used their photometry
at 3.4 and 4.6 $\mu$m to create an extrapolated spectra out to 5$\mu$m, which
we used to estimate NIRCam photometry, following Finkelstein et al. (2023). We
supplemented these with empirical NIRCAM SEDs of M dwarfs, obtained from a
selection of extremely compact objects in F115W-F200W color magnitude space,
consistent with stellar evolutionary models and JWST observations of globular
clusters (Weisz et al., 2023, B. Johnson priv. comm). The full set of model
photometry were then fit to the observed NIRCam $0.2^{\prime\prime}$ diameter
aperture photometry for the $z>8$ candidate galaxies using a $\chi^{2}$
minimization approach. We compared the resulting $\chi^{2}$ minima for the
stellar fits to those from the EAZY galaxy templates, and if an object had a
$\Delta\chi^{2}<4$ between the galaxy model fit and the stellar fit, it was
flagged as a brown dwarf candidate.

We find 303 objects in our $z>8$ sample with $\Delta\chi^{2}>4$ that are
unresolved (42% of the full $z>8$, $\Delta\chi^{2}>4$ sample), with a half-
light radius less than $0.063^{\prime\prime}$, while only six objects across
both fields have fits to stellar models with EAZY $\chi^{2}_{\mathrm{min}}$
within $\Delta\chi^{2}<4$ (two of these sources have lower $\chi^{2}$ values
with the brown dwarf fits). We flag the sources in the online table if they
satisfy either of these requirements. Of these objects, only two sources are
both unresolved and have stellar fits within $\Delta\chi^{2}<4$: JADES-
GS-53.0353-27.87776 ($z_{a}=10.82$) and JADES-GN-189.19772+62.25697
($z_{a}=8.61$). The latter source, which is detected with HST WFC3/IR, was
identified as the Y-dropout candidate GNDY-6474515254 in Bouwens et al.
(2015). While this object has evidence for being a brown dwarf, FRESCO
identified both [OIII]$\lambda\lambda$5007,4959 emission lines
($z_{spec}=8.28$), ruling out the brown dwarf hypothesis.

There are additional brown dwarf candidates in the $z>8$ candidate galaxies
with $\Delta\chi^{2}<4$ identified in §4.4. We find 83 objects with an F444W
half-light radius less than $0.063^{\prime\prime}$, and 17 objects with
stellar fits within $\Delta\chi^{2}<4$ (6 of these sources have lower
$\chi^{2}$ values with the brown dwarf fits). We caution that because of the
larger flux uncertainties for these objects, it is more likely that models
would fit these data with comparable $\chi^{2}$ values, but we include flags
in the online table in these cases. Only five of the sources in this subsample
are unresolved with comparable brown dwarf fits to the EAZY fits: JADES-
GS+53.02588-27.87203 ($z_{a}=8.84$), JADES-GS+53.12444-27.81363
($z_{a}=8.33$), JADES-GS+53.07645-27.84677 ($z_{a}=8.64$), JADES-
GN+189.16606+62.31433 ($z_{a}=8.6$), and JADES-GN+189.07787+62.23302
($z_{a}=8.1$). These sources, on visual inspection, do not appear to be strong
brown dwarf candidates due to them being quite faint, which would indicate
potentially unphysical distances compared to models of the halo brown dwarf
population (Ryan et al., 2005). While there are 19 unresolved sources in the
sample that are proximate to brighter objects (as in Section 4.5), none of
these have stellar fits within $\Delta\chi^{2}<4$ of the EAZY fits.

###  4.7 $z>8$ Candidates in the Literature

As the GOODS-S and GOODS-N fields have been observed across a wide wavelength
range and to deep observational flux limits, a number of the sources in our
sample have been previously presented in the literature. As described in
Robertson et al. (2023), both JADES-GS-z10-0 (JADES-GS-53.15883-27.7735) and
JADES-GS-z11-0 (JADES-GS-53.16476-27.77463) were previously identified in
Bouwens et al. (2011b), as UDFj-38116243 and UDFj-39546284, respectively. Both
of these galaxies are in our $z>8$ sample, as JADES-GS-53.15883-27.7735 and
JADES-GS-53.16476-27.77463. Similarly, we also previously discussed GN-z11,
first identified in Bouwens et al. (2010), and later further explored in Oesch
et al. (2014, 2016), which is present in our sample as JADES-
GN-189.10605+62.24205.

In Bouwens et al. (2023), the authors use the publicly available JEMS data to
search for $z>8$ candidates in GOODS-S and construct a sample of ten sources.
Nine of the ten sources appear in our sample (their source XDFY-2376346017,
which they measure at $z_{EAZY}=8.3^{+0.2}_{-0.2}$, is at $z_{a}=7.89$ in our
fits, and we additionally measure a FRESCO $z_{spec}=7.975$ for this source),
and of those, eight sources were previously known and are in our sample. The
remaining two sources were not previously known, and also appear in our
sample: JADES-GS-53.13918-27.78273 ($z_{a}=10.49$) and JADES-
GS-53.16863-27.79276 ($z_{a}=11.71$). Donnan et al. (2023) perform a similar
search, and find two additional candidates that fall into our sample: JADES-
GS-53.17551-27.78064 ($z_{a}=9.66$), and JADES-GS-53.12166-27.83012
($z_{a}=9.42$) (they also independently recover JADES-GS-53.16863-27.79276).
The photometric redshifts presented in Bouwens et al. (2023) for JADES-
GS-53.13918-27.78273 (XDFH-2334046578 in their sample,
$z_{EAZY}=11.8^{+0.4}_{-0.5}$) and JADES-GS-53.16863-27.79276 (XDFJ-2404647339
in their sample, $z_{EAZY}=11.4^{+0.4}_{-0.5}$) are broadly similar to our
values, but we measure a much lower redshift for the former due to the
availability of the F150W flux from JADES. Similarly, Donnan et al. (2023),
estimate similar photometric redshifts to what we find for JADES-
GS-53.17551-27.78064 (UDF-21003 in their sample,
$z_{phot}=9.79^{+0.15}_{-0.13}$) and JADES-GS-53.16863-27.79276 (UDF 16748 in
their sample, $z_{phot}=11.77^{+0.29}_{-0.44}$), but they claim a much higher
redshift for JADES-GS-53.12166-27.83012 (UDF-3216 in their sample,
$z_{phot}=12.56^{+0.64}_{-0.66}$), which is inconsistent with the measured
F150W flux. We note that this latter candidate appears in our catalog of
sources proximate to brighter objects, although with $\Delta\chi^{2}=4.32$.

For the full sample of $\Delta\chi^{2}>4$ candidates at $z>8$, we additionally
cross-matched their sky positions against GOODS-S and GOODS-N high-redshift
catalogs in the literature, including Bunker & Wilkins (2009); Bunker et al.
(2010); Yan et al. (2010); Bouwens et al. (2011b); Lorenzoni et al. (2011);
Ellis et al. (2013); Lorenzoni et al. (2013); McLure et al. (2013); Oesch et
al. (2013); Schenker et al. (2013); Oesch et al. (2014); Bouwens et al.
(2015); Finkelstein et al. (2015); Bouwens et al. (2016); Harikane et al.
(2016) and Bouwens et al. (2021). Because our JADES mosaics were aligned using
the GAIA reference frame, we had to carefully visually match against each
sample, which have different reference frames. In Table 4, we list the targets
that were matched to sources previously discussed in the literature, the
photometric redshift for these sources, and we include the references for each
object.

We find 47 objects across the full $\Delta\chi^{2}>4$ catalog have been
discussed previously in the literature, 42 in GOODS-S and 5 in GOODS-N. As
previously mentioned seven are at $z_{a}>10$, three are at $z_{a}=9-10$, and
the remaining 37 are at $z_{a}=8-9$.

Table 4: $\Delta\chi^{2}>4$ Catalog Sources in the Literature.

JADES ID |  EAZY $z_{a}$ | Reference(s)
---|---|---
JADES-GS-53.15751-27.76677 | $8.00$ | 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 16
JADES-GS-53.16415-27.78452 | $8.02$ | 8, 10
JADES-GS-53.13563-27.79185 | $8.02$ | 12, 16
JADES-GN-189.27457+62.21053a | $8.03$ | 12
JADES-GS-53.08174-27.89883 | $8.04$ | 15
JADES-GS-53.13849-27.85854 | $8.04$ | 12, 16
JADES-GS-53.148-27.79571 | $8.04$ | 4, 10, 12, 15, 16
JADES-GS-53.06029-27.86353 | $8.04$ | 12, 13, 16
JADES-GS-53.17727-27.78011 | $8.08$ | 8, 12, 15, 16
JADES-GS-53.13675-27.83746 | $8.13$ | 13
JADES-GS-53.08745-27.81492 | $8.17$ | 7, 12, 16
JADES-GS-53.06035-27.86355 | $8.17$ | 12, 13, 16
JADES-GS-53.07052-27.86725 | $8.21$ | 12, 16
JADES-GS-53.05924-27.8353 | $8.22$ | 12, 16
JADES-GS-53.1459-27.82279 | $8.23$ | 8
JADES-GS-53.13569-27.83884 | $8.24$ | 13
JADES-GN-189.2032+62.24245 | $8.28$ | 12
JADES-GS-53.14585-27.82274 | $8.28$ | 8
JADES-GS-53.10393-27.89059 | $8.35$ | 12, 16
JADES-GS-53.20988-27.77928 | $8.36$ | 12, 16
JADES-GN-189.09186+62.25744 | $8.38$ | 12
JADES-GS-53.1571-27.83708 | $8.39$ | 12, 15, 16
JADES-GS-53.08738-27.86033 | $8.46$ | 8, 12, 13, 16
JADES-GS-53.10224-27.85925 | $8.46$ | 12
JADES-GS-53.16447-27.80218 | $8.50$ | 4, 6, 8, 9, 13, 16, 19
JADES-GS-53.0865-27.8592 | $8.50$ | 12, 16
JADES-GS-53.08741-27.8604 | $8.51$ | 8, 12, 13, 16
JADES-GS-53.15891-27.76508 | $8.52$ | 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 13, 16, 19
JADES-GS-53.08932-27.8727 | $8.53$ | 8, 13
JADES-GS-53.1777-27.78478 | $8.53$ | 6, 8, 9, 19
JADES-GS-53.07581-27.87938 | $8.55$ | 8, 12, 13, 16
JADES-GS-53.15784-27.76271 | $8.57$ | 12, 16
JADES-GN-189.19772+62.25697 | $8.61$ | 12, 13, 16
JADES-GS-53.16767-27.80017 | $8.64$ | 9, 12, 14, 16, 19
JADES-GS-53.16337-27.77569 | $8.65$ | 6, 8, 9, 10, 12, 16, 19
JADES-GS-53.15342-27.77844 | $8.81$ | 10
JADES-GN-189.2114+62.1703 | $8.92$ | 12, 16
JADES-GS-53.13363-27.84499 | $9.36$ | 14, 16
JADES-GS-53.12166-27.83012a | $9.42$ | 20
JADES-GS-53.17551-27.78064 | $9.66$ | 20
JADES-GS-53.13918-27.78273 | $10.49$ | 19
JADES-GS-53.15883-27.7735b | $10.84$ | 6, 9, 12, 14, 16, 17, 18, 19, 20
JADES-GN-189.10604+62.24204c | $11.00$ | 11, 12, 14, 16
JADES-GS-53.16863-27.79276 | $11.71$ | 19, 20
JADES-GS-53.16476-27.77463d | $12.31$ | 6, 8, 17, 18, 19, 20
JADES-GS-53.16635-27.82156e | $12.46$ | 17, 18, 21
JADES-GS-53.14988-27.7765f | $13.41$ | 17, 18

Note. — a: Proximate to a brighter source, as described in §4.5, b: JADES-
GS-z10-0, c: GN-z11, d: JADES-GS-z11-0, e: JADES-GS-z12-0, f: JADES-GS-z13-0,
References: 1: Bunker & Wilkins (2009), 2: Bunker et al. (2010), 3: Yan et al.
(2010), 4: Bouwens et al. (2011b), 5: Lorenzoni et al. (2011), 6: Ellis et al.
(2013), 7: Lorenzoni et al. (2013), 8: McLure et al. (2013), 9: Oesch et al.
(2013), 10: Schenker et al. (2013), 11: Oesch et al. (2014), 12: Bouwens et
al. (2015), 13: Finkelstein et al. (2015), 14: Bouwens et al. (2016), 15:
Harikane et al. (2016), 16: Bouwens et al. (2021), 17: Curtis-Lake et al.
(2023), 18: Robertson et al. (2023), 19: Bouwens et al. (2023), 20: Donnan et
al. (2023), 20: D’Eugenio et al. (2023).

###  4.8 Alternate EAZY Template Fitting Results

In Larson et al. (2023), the authors present a series of theoretical galaxy
templates222https://ceers.github.io/LarsonSEDTemplates designed to be used
with EAZY to better model the bluer UV slopes expected for very high redshift
galaxies. To create these templates, the authors first used EAZY to calculate
photometric redshifts for mock galaxies in the CEERS Simulated Data Product
V32 catalog using the EAZY “tweak_fsps_QSF_v12_v3” templates, which were
derived from fsps. At this point, the authors created an additional set of
templates that better matched the simulated $m_{F200W}-m_{F277W}$ colors for
the $z>8$ galaxies in their sample using the binary stellar evolution models
BPASS (Eldridge et al., 2017) with nebular emission derived from the spectral
synthesis code CLOUDY (Ferland et al., 2017). These templates resulted in
significantly better photometric redshift estimations for the mock galaxies
with the CEERS filter set.

To explore how our choice of EAZY templates affects our final $z>8$ sample, we
fit the photometry for all of the objects recovered across GOODS-N and GOODS-S
with EAZY with the recommended template set from Larson et al. (2023) for
fitting $z>8$ galaxies: tweak_fsps_QSF_v12_v3 along with the BPASS-only “Set
1” and the “BPASS + CLOUDY – NO LyA” “Set 4” templates. We ran EAZY in an
otherwise identical manner, including the template error function used, but we
utilized the same photometric offsets as provided in Table 2.

The resulting photometric redshifts for our primary sample of $z>8$ sources
provide no significant differences or noticeably improved photometric redshift
fits: only 4% have $|z_{Larson}-z_{a}|/(1+z_{a})>0.15$ (23 sources in GOODS-S
and 5 sources in in GOODS-N). More importantly, if we look at those sources
where $z_{Larson}<8$, only 2.5% (14 sources in GOODS-S and 4 sources in
GOODS-N) have significantly different photometric redshifts. In the majority
of these cases, the lower-redshift solution offered by the Larson et al.
(2023) templates is at the same secondary $\chi^{2}$ minimum seen for our own
template fits, and the validity of the fit is strongly dependent on the
observed F090W or F115W fluxes.

The sources in our sample with $\Delta\chi^{2}<4$ fits are less robust, as has
previously been discussed, and show more discrepancy between the fits with our
EAZY templates and those from Larson et al. (2023). Here, 37% have
$|z_{Larson}-z_{a}|/(1+z_{a})>0.15$ (67 sources in GOODS-S and 17 sources in
in GOODS-N). 64 of these GOODS-S sources and 15 of the GOODS-N sources (for a
total fraction of 35% of the $\Delta\chi^{2}<4$ objects) have $z_{Larson}<8$.

In addition, we derived a sample of $z_{a}>8$ sources from fits with the
Larson et al. (2023) templates after applying the same SNR, $P(z>7)$ and
$\Delta\chi^{2}$ cuts as described in §3.2. We compared the resulting
candidates with those from the original template set, and after visual
inspection found a total of 10 additional $z>8$ candidates (7 in GOODS-S and 3
in GOODS-N) which we list in Table 6. Of those sources, 5 are at $z_{a}=6-8$
and 2 have $P(z<7)<0.7$ in our own EAZY fits. The remaining three objects are
quite faint, but should be considered alongside the main sample. We conclude
that our results would not be significantly improved by using the Larson et
al. (2023) templates.

###  4.9 Spectroscopic Redshifts

In total, we have spectroscopic redshifts for 42 objects in our sample. As
discussed previously, five of the high-redshift galaxies have been
spectroscopically confirmed to lie at $z>10$: JADES-GS-z10-0, JADES-GS-z11-0,
JADES-GS-z12-0, JADES-GS-z13-0 (Curtis-Lake et al., 2023; D’Eugenio et al.,
2023), and GN-z11 (Bunker et al., 2023b). In this section, we discuss the
other objects in our sample with spectroscopic confirmation from both JWST
NIRSpec and JWST NIRCam grism spectroscopy from FRESCO. We also compare the
photometric redshifts to the spectroscopic redshifts and discuss the observed
offset between the two values. Four additional GOODS-S sources have NIRspec
spectroscopic redshifts at $z>8$. Besides GN-z11, there are no GOODS-N NIRSpec
spectroscopic redshifts for our sample. An additional 28 sources in our sample
have FRESCO spectroscopic redshifts, with 19 objects in GOODS-S and 8 in
GOODS-N. As described in Section 4.5, there are 4 additional GOODS-S sources,
and 1 GOODS-N object with FRESCO $z_{spec}$ that are proximate to other bright
sources. The photometric redshifts for these sources were derived from either
single [OIII]$\lambda 5007$ line detections or, in some brighter cases,
multiple line detections. Fifteen of the sources in our sample of $z>8$
candidates have FRESCO spectroscopic redshifts at $z<8$ (13 in GOODS-S, and 1
in GOODS-N) in all cases at $z_{spec}>7.6$. We chose to include these objects
as they satisfy our EAZY selection criteria.

In Figure 10 we show the spectroscopic redshifts of the objects in our sample
against their photometric redshift. There are no catastrophic outliers,
defined here as those objects where $|z_{spec}-z_{a}|/(1+z_{spec})>0.15$. As
discussed previously with individual objects, the photometric redshifts have a
systematic offset such that EAZY is slightly overpredicting the distances to
these galaxies ($\langle\Delta z=z_{a}-z_{spec}\rangle=0.26$). To estimate the
scatter on the relationship, we also calculated the normalized mean absolute
deviation $\sigma_{NMAD}$, defined as:

$\sigma_{\mathrm{NMAD}}=1.48\times\mathrm{median}\left(\left|\frac{\delta
z-\mathrm{median}(\delta z)}{1+z_{spec}}\right|\right)$ (1)

where $\delta z=z_{spec}-z_{phot}$. For all of our sources with spectroscopic
redshifts, $\sigma_{NMAD}=0.05$. Understanding the source of this offset is
quite important given the usage of photometric redshifts in deriving
statistical parameters like the UV luminosity function. By constraining the
EAZY fit for each of these sources to be at the spectroscopic redshift, we
find that the primary reason for these higher-redshift fits is due to the flux
of the filter that spans the Lyman-$\alpha$ break. In the fits where redshift
is constrained to be at $z_{spec}$, the observed fluxes in the band at the
Lyman-$\alpha$ break are overestimated in the template fits. While this effect
maybe be due to photometric scatter upwards in those bands, it is more likely
due to the templates themselves. In Arrabal Haro et al. (2023b), the authors
present $z_{spec}=8-10$ objects with NIRSpec spectroscopy which show a larger
offset ($\langle\Delta z=z_{a}-z_{spec}\rangle=0.46\pm 0.11$) to higher
photometric redshifts, and these authors also hypothesize that this might be a
result of potential differences between the observed high-redshift galaxy SEDs
and the templates used to model high-redshift galaxies.

One potential source of excess flux in the UV is the strength of the
Lyman-$\alpha$ emission line in our templates. To explore the effect of this
line, we first took our EAZY templates and removed the Lyman-$\alpha$
contribution by cutting out the flux between 1170 to 1290 Å and replacing that
portion in each template with a linear fit. Using these templates without
Lyman-$\alpha$, we re-fit every one of our sources with spectroscopic
redshifts, and calculated a new $\sigma_{NMAD}=0.02$, as well as a difference
in the average offset $\langle\Delta z=z_{a}-z_{spec}\rangle=0.19$. While this
is smaller, the offset is still present, indicating that Lyman-$\alpha$ flux
is not the dominant factor. One alternate possibility is that the strength of
the optical emission lines at long wavelength may not be fully reflected in
our limited template set, and for those $z_{spec}<9$ sources (where the
optical emission is not redshifted out of the NIRCam filters), this may have
an effect of pushing fits at higher redshifts. At the redshift range of our
sample, the FRESCO redshifts are calculated preferentially for those objects
with strong line emission, which may not be probed by our template set.
Understanding this offset may prove important for future fits to high-redshift
galaxies, and it will necessitate the creation of templates derived from high-
resolution NIRSpec spectra of these sources once larger samples are observed.

Figure 10: (Left) Spectroscopic Redshifts for objects in our sample measured
from both NIRSpec (square symbols) and FRESCO (circular symbols) spectroscopy,
as compared to the EAZY photometric redshifts. We highlight those four sources
proximate to brighter sources, as discussed in Section 4.5, with black filled
circles. (Right) A zoom in on the dashed region at $z=7-9$ in the left panel.
We find that the estimated photometric redshifts overpredict the spectroscopic
redshifts ($\langle\Delta z=z_{a}-z_{spec}\rangle=0.26$), potentially due to
the differences between our adopted templates and high-redshift galaxies. We
explored removing Lyman-$\alpha$ emission in our template set, and this lowers
the offset to $\langle\Delta z=z_{spec}-z_{a}\rangle=0.19$.

###  4.10 Rejected High-Redshift Candidates

Example Visually Rejected Candidates

Figure 11:  Example SEDs for four rejected GOODS-S and GOODS-N galaxies. In
each panel, the colors, lines, and symbols are as in Figure 2.

Finding and characterizing high-redshift galaxies is a complex process, even
given the IR filters on board JWST. In our visual inspection, we found a
number of bright galaxies that we rejected from our $z>8$ sample because of
multiple reasons, and in this section, we will provide four examples as case
studies to demonstrate the sorts of galaxies with colors that can mimic those
of high-redshift galaxies. This analysis follows discussions in Naidu et al.
(2022) and Zavala et al. (2023), and seen directly with CEERS-93316, a
candidate galaxy at $z_{phot}=16.4$ which was shown to be at $z_{spec}=4.912$
(Arrabal Haro et al., 2023a).

In Figure 11 we provide SEDs for JADES-GS-53.0143-27.88355, JADES-
GS-53.08294-27.85563, JADES-GS-53.20055-27.78493, and JADES-
GN-189.30986+62.20844. Here, we highlight the solution at $z<7$ in each, while
also leaving the overall minimum $\chi^{2}$ solution.

JADES-GS-53.0143-27.88355 ($m_{Kron,AB}=29.3$), appears from the thumbnails
and from the EAZY minimum $\chi^{2}$ fit to be an F150W dropout at
$z_{a}=12.51$. However, the red UV slope indicates that perhaps this object is
much dustier and at low-redshift ($z_{alt}=3.41$), where the H$\alpha$
emission line was boosting the observed F277W flux. This UV slope could also
arise from the bright source to the southeast (at $z_{spec}=0.2472$, Cooper et
al., 2012). In addition there is what appears to be a flux detection in the
F115W thumbnail which helps to rule out the high-redshift solution.

JADES-GS-53.08294-27.85563 ($m_{F277W,Kron}=26.8$) appears to be a bright
F150W dropout clump immediately adjacent to another object. The SED is well
fit at $z_{a}=14.51$, and the fit constrained to be at $z<7$ is significantly
worse ($z_{alt}=3.56$). The secondary source, which is detected with all five
of the JADES HST/ACS bands (although only at $2\sigma$ significance for
F435W), has an EAZY template redshift $z_{a}=3.4$. This redshift puts the
Balmer break between the NIRCam F150W and F200W filters, and we cannot rule
out the possibility that this is what we are observing for JADES-
GS-53.08294-27.85563. This source appeared in a sample of “HST dark” galaxies
in Williams et al. (2023b), where they present a photometric redshift of
$z_{\mathrm{phot}}=3.38$, although they use a larger aperture for measuring
photometry which may introduce flux from the nearby source. JADES-
GS-53.08294-27.85563 was further imaged in six NIRCam medium-band filters as
part of the JWST Cycle-2 GO observations of the JADES Origins Field (JOF, PID
3215; Eisenstein et al., 2023b), and a more detailed analysis of this source
will be presented in a forthcoming paper from the collaboration (Robertson, B.
et al. in prep.). Both sources will be observed by the NIRSpec prism in JWST
GTO program 1287 (Willott, C. in prep).

JADES-GS-53.20055-27.78493 ($m_{F277W,Kron}=28.8$) appears to be an F200W
dropout at $z_{a}=15.89$ southeast of another, brighter source. While positive
flux is observed at the 1 - 2 nJy level in F115W and F150W, this is at a SNR
$<0.8$ in both cases. This source was ruled out as an F200W dropout because of
the detection at the 4$\sigma$ of F090W flux, which can be seen in the
thumbnail.

JADES-GN-189.30986+62.20844 ($m_{F277W,Kron}=27.4$) is best fit at
$z_{a}=11.36$, placing the observed Lyman-$\alpha$ break at 1.5$\mu$m. This
object is proximate to another, brighter galaxy with an EAZY fit at
$z_{a}=1.87$ with a complex morphology first observed as part of the GOODS
survey in Giavalisco et al. (2004). This is at a lower redshift than the
alternate EAZY result for JADES-GN-189.30986+62.20844, $z_{a}=2.58$, but the
faint F115W detection (SNR = 3.64) demonstrates that the minimum $\chi^{2}$
redshift solution for this object is erroneous.

##  5 Discussion

In this section we explore the selection and derived properties of this large
sample of candidate high-redshift galaxies in more detail. A full description
of the theoretical implications of these sources is outside the scope of this
paper. The stellar mass and star formation histories for these sources will be
the focus of a study by Tacchella et al. (in prep), while the full estimation
of the evolution of the UV luminosity function at $z>8$ from the JADES sources
will be presented in Whitler et al. (in prep).

###  5.1 UV Magnitudes

Figure 12: MUV plotted against the best-fitting EAZY $z_{a}$ photometric
redshift or the observed spectroscopic redshift for the $z>8$ galaxies and
candidate galaxies in the GOODS-S (blue) and GOODS-N (red) $z>8$ samples. The
points and colors are the same as Figure 4. On the right we show the UV
magnitude distribution. GN-z11 stands out for its extreme $M_{UV}$.

We calculated the UV magnitudes from the EAZY fits to explore the range of
intrinsic UV brightnesses for the sample. To calculate $M_{UV}$ we started by
fitting the Kron magnitude catalog fluxes forced to be at the redshifts
derived from the smaller circular apertures, or, if available, the
spectroscopic redshifts for each source. This was done to not bias the
resulting UV magnitudes against more extended objects by encompassing more of
the total flux. From here, we took the best-fitting rest-frame EAZY template
for each object and passed it through mock top-hat filter centered at $1500$Å
with a width of $100$Å, and calculated the intrinsic UV magnitude based on the
resulting flux.

In Figure 12 we show the resulting $M_{UV}$ values against the photometric and
spectroscopic redshift for the sample. As can be expected, GN-z11 is by far
the brightest source in the sample at $M_{UV}=-22.0$333In Bunker et al.
(2023b), the authors calculate $M_{UV}=-21.5$ for GN-z11 from JWST/NIRSpec
spectroscopy for the source, and in Tacchella et al. (2023) the authors
present a value of $M_{UV}=-21.6$ from the ForcePho fits to the NIRCam
photometry to the source. Our value is higher due to the fact that we
estimated $M_{UV}$ from the Kron magnitudes to the source, which includes
excess flux from a “haze” observed near the source (Tacchella et al., 2023).
The Kron fluxes we use are $\sim 1.5$ times brigher than what are presented in
Tacchella et al. (2023), and if we scale our fluxes by this amount our value
changes to $M_{UV}=-21.58$ for GN-z11.. Excitingly, we find 227 objects in our
sample with $M_{UV}>-18$, and 16 objects (all in GOODS-S) with $M_{UV}>-17$,
entirely at $z_{a}<11.5$. These UV-faint high-redshift galaxy candidates
demonstrate the extraordinary depth of the JADES survey. In addition, these
results stand in contrast to the decline in the number counts of HST-observed
galaxies discussed in Oesch et al. (2018) and Bouwens et al. (2019), and help
to confirm results from other JWST surveys (Finkelstein et al., 2023; Harikane
et al., 2023; Pérez-González et al., 2023).

###  5.2 Dropout Colors

As discussed in the introduction, traditionally, high-redshift samples are
assembled by targeting Lyman-$\alpha$ dropout galaxies in color space. In
Hainline et al. (2020), the authors used the JAGUAR mock catalog (Williams et
al., 2018) to explore the NIRCam colors of simulated dropout samples, and
demonstrated the tradeoff between sample completeness and accuracy for high-
redshift dropout galaxies. Because of the utility of dropout selection, we
sought to explore how successful this technique alone would be at finding the
JADES $z>8$ candidate galaxies. We utilized a uniform two-color selection
scheme to target F090W, F115W, and F150W dropouts within our primary $z>8$
sample, where in each case the color limit for the filters that targeted the
Lyman-$\alpha$ break was $m_{1}-m_{2}>1.0$, while the color limit for the
filters that targeted the rest-frame UV was $m_{2}-m_{3}<0.5$.

Figure 13:  (Top Row) F090W, F115W, and F150W color selection diagrams for the
GOODS-S and GOODS-N $z>8$ sample. We show all of the sources in each panel,
with upward pointing arrows plotted for those whose colors place them off the
top of each figure. The colored region indicates the simple dropout selection
in each panel, and we indicate which sources are selected with thick lines
around the symbol. (Bottom Row) Photometric redshift distribution for the
$z>8$ sample plotted with a thick grey line, with the photometric redshifts
for each color-selected samples overplotted in colored regions. In black, we
plot the sum of all three of the dropout distributions. While the F090W,
F115W, and F150W dropouts broadly map to photometric redshifts of $z=8-8.5$,
$z=8.5-11.5$, and $z=11.5-15$ respectively, there are a large number of
sources in our sample that would not be selected via color selection, as seen
by comparing the black and grey histograms.

In Figure 13, we show the F090W, F115W, and F150W color selection in the top
row plots, targeting the entire $z>8$ sample in each panel. In the bottom
panel we show a photometric redshift histogram for the sources in the sample
with a thick grey line and, in the shaded regions the F090W, F115W, and F150W
dropout sample distributions. We sum these distributions and plot that with a
thick black line. The lone F090W dropout at $z_{a}>15$ is JADES-
GS-53.12692-27.79102, which we discuss in Section 4.3 and plot in the upper-
right panel of Figure 8. We find that $71\%$ of the $z>8$ sample would be
selected as dropouts with these color criteria, while 171 GOODS-S and 37
GOODS-N objects in the sample are not selected by any scheme, which are are
predominantly at $z\sim 8.5$ and $z\sim 11.5$, as seen from the bottom panel
of the figure. These candidates have colors just outside of the selected color
space, where $z\sim 8.5$, while $m_{F090W}-m_{F115W}>1.0$,
$m_{F115W}-m_{F150W}=0.5-1.0$. A similar effect is seen for the F115W and
F150W dropouts at $z\sim 11.5$. This effect could be mitigated by expanding
the selection criteria, but this is at the risk of including significantly
more lower-redshift interlopers (Hainline et al., 2020).

Another way of looking at color selection is by directly plotting the dropout
color against the EAZY photometric redshift. At $z_{phot}=8$, the
Lyman-$\alpha$ break is at $\sim 1.1\mu$m, which is on the blue edge of the
NIRCam F115W band, and by $z_{phot}=10$, the Lyman-$\alpha$ break should sit
between the F115W and F150W filters, so for the objects at increasing
photometric redshifts in this range, the F115W SNR will vary as the galaxy’s
rest-frame UV emission drops out of this band. In Figure 14, we plot the
$m_{F115W}-m_{F150W}$ color against the EAZY $z_{a}$ value for the GOODS-N and
GOODS-S objects at $z_{phot}=8-10$. As expected, the $m_{F115W}-m_{F150W}$
color increases in this redshift range. We find that 95% of the candidate
high-redshift galaxies selected as F115W dropouts by our cuts have
$z_{a}>8.75$, while 16% of the candidates at $z_{a}=8.75-10.0$ in our sample
would still fall outside of this simple color cut.

Figure 14: $m_{F115W}-m_{F150W}$ color, as measured using $0.2^{\prime\prime}$
diameter aperture photometry, plotted against the best-fitting EAZY $z_{a}$
photometric redshift for the GOODS-S (blue) and GOODS-N (red) samples. As
photometric redshift increases, the effect of the Lyman-$\alpha$ break can be
seen in the redder $m_{F115W}-m_{F115W}$ color. We shade the region and
highlight those objects selected by a $m_{F115W}-m_{F150W}>1.0$ and
$m_{F150W}-m_{F200W}<0.5$ color cut with a thick outline around the point.

###  5.3 Using $\Delta\chi^{2}$ to Discern Between High- and Low-Redshift
Template-fitting Solutions

Fitting a galaxy’s SED with templates or stellar population synthesis models
enables a measurement of the probability of a galaxy being at a range of
photometric redshifts. In this study, we have used the difference in
$\chi^{2}$ values between the best-fit model and the model constrained to be
at $z<7$ as a our metric of accuracy. The exact $\Delta\chi^{2}$ value we
measure for each object is dependent on the template set used, as well as the
flux uncertainties and, in our case, the template error function and
photometric offsets used. As a result, as is the case for any continuous value
of merit, choosing a specific cut is a tradeoff between sample accuracy and
completeness.

In Harikane et al. (2023), the authors discuss that $\Delta\chi^{2}>4$, the
value we adopt in this current work (following Bowler et al., 2020; Donnan et
al., 2023; Finkelstein et al., 2023; Harikane et al., 2022) is not sufficient
for properly removing low-redshift interlopers, through injecting and
recovering mock galaxies in the CEERS extragalactic data. Instead, these
authors recommend the stricter cut of $\Delta\chi^{2}>9$. Because we have a
larger number of observed photometric filter in the JADES data, choosing a low
$\Delta\chi^{2}$ limit may be resulting in the inclusion of more potential
interlopers, which has lead to our releasing output catalogs which include all
of the sources we visually inspected regardless of the chosen $\Delta\chi^{2}$
cut.

If we do instead look only at those objects in our sample with
$\Delta\chi^{2}>9$, our primary sample is reduced to 483 candidates (358 in
GOODS-S and 125 in GOODS-N), or 67% of the 717 $\Delta\chi^{2}>4$ sources (67%
in GOODS-S and 69% in GOODS-N). This subsample selected with a stricter cut
has a similar redshift distribution to our full sample (19 of the 33
candidates at $z>12$ would still be included), but the sources have brighter
F277W magnitudes, as would be expected. The median F277W magnitude for the
$\Delta\chi^{2}>4$ sample is 29.11, while the median F277W magnitude for the
$\Delta\chi^{2}>9$ sample is 28.96. It should be noted that every source in
our sample with a spectroscopic redshift has $\Delta\chi^{2}>13$. Pushing the
cut to even stricter values, we find that 45% of the original sample has
$\Delta\chi^{2}>15$ and 36% of the original sample has $\Delta\chi^{2}>20$.

###  5.4 Candidate Galaxies with Red Long-Wavelength Slopes

In our visual inspection of the galaxy candidates, we find a number of high-
redshift candidates with very red long-wavelength slopes, following the
discovery of similar sources at $z_{phot}=5-9$ in Furtak et al. (2023), Barro
et al. (2023), Labbé et al. (2023), Endsley et al. (2023) Leung et al. (2023),
Akins et al. (2023), and Williams et al. (2023b). These objects are often very
bright and unresolved in F444W, and in many cases are comparatively faint at
shorter wavelengths. To systematically search for these sources in our full
sample, we selected those objects that have $m_{F277W}-m_{F444W}>1.3$ and
$m_{200W}-m_{F356W}>0.0$. These color limits ensure that the observed red
long-wavelength slope is not due to an emission line boosting the F444W flux,
and return sources similar to those presented in the literature.

Example Red Long-Wavelength Slope Candidates

Figure 15:  Example SEDs for six candidate galaxies with red long-wavelength
slopes. In each panel, the colors, lines, and symbols are as in Figure 2.

For our sample, these cuts select 12 objects (9 in GOODS-S and 3 in GOODS-N).
Of those sources, 11 are at $z_{a}=8-10$, while one source is at
$z_{a}=11.64$. We provide the IDs, $z_{a}$ values, F444W magnitudes (measured
in an $0.2^{\prime\prime}$ aperture), and colors for these sources in Table 5,
and we show six of these sources in Figure 15. Outside of the highest-redshift
source, JADES-GS-53.11023-27.74928, these sources have fairly tight lower
limits on their redshift due to both the lack of flux observed in the F090W
band and the red slope not being easily reproduced at low redshift. The EAZY
templates used in the present analysis are able to fit the observed SEDs as
high-redshift sources, as is demonstrated with the blue lines in Figure 15.
However, JADES-GS-53.11023-27.74928 is very faint ($\sim 1$ nJy) at
wavelengths shorter than 2$\mu$m, making a photometric redshift estimate
difficult. JADES-GS-53.18354-27.77014, a source with a FRESCO spectroscopic
redshift ($z_{spec}=8.38$) is extended with three visible clumps spanning
$0.6^{\prime\prime}$ (2.9 kpc at $z_{a}=8.38$), of which the central knot has
a very observed red UV through optical slope.

Table 5: Sources with Red Long-Wavelength Slopes

JADES ID |  EAZY $z_{a}$ | $m_{F444W}$ | $m_{F277W}-m_{F444W}$ | $m_{F200W}-m_{F356W}$
---|---|---|---|---
JADES-GN-189.05064+62.27935 | $8.04$ | 27.63 | 1.495 | 0.209
JADES-GS-53.04601-27.85399 | $8.3$ | 26.44 | 1.493 | 0.602
JADES-GS-53.19904-27.77207 | $8.31$ | 29.14 | 1.313 | 0.182
JADES-GS-53.19211-27.75252 | $8.53^{a}$ | 26.79 | 1.354 | 0.608
JADES-GN-189.18036+62.28851 | $8.69$ | 28.42 | 1.51 | 1.021
JADES-GS-53.18392-27.78691 | $8.71$ | 28.14 | 1.76 | 0.907
JADES-GS-53.1387-27.79248 | $8.87$ | 28.4 | 1.88 | 0.475
JADES-GN-189.17121+62.21476 | $8.91^{b}$ | 26.41 | 1.514 | 0.535
JADES-GS-53.18354-27.77014 | $8.95^{c}$ | 27.04 | 1.529 | 0.506
JADES-GS-53.18087-27.80577 | $9.33$ | 29.42 | 1.414 | 0.185
JADES-GS-53.18448-27.79696 | $9.66$ | 28.8 | 1.355 | 1.783
JADES-GS-53.11023-27.74928 | $11.64$ | 28.52 | 1.339 | 0.372

Note. — a: $z_{spec}=7.99$, b: $z_{spec}=8.62$, c: $z_{spec}=8.38$

The origin of these sources is not obvious. One possible cause of such a red
slope is the presence of a dust-obscured accretion disk from supermassive
black hole growth in these objects, as discussed in Furtak et al. (2023),
Barro et al. (2023) and Akins et al. (2023). This would be of interest given
the lack of ultra-high-redshift active galaxies currently known, and the short
timescales by which these supermassive black holes could have grown in the
early universe. Another alternative is that these sources could have strong
optical line emission that boosts the long-wavelength flux, similar to what is
presented in Endsley et al. (2023). In this work, the authors describe how
galaxy models with young stellar populations or supermassive black hole growth
can replicate the photometry for a sample of sources selected from JWST CEERS.
An alternate view is offered in Labbé et al. (2023), who argue that sources
like these are instead very massive, and the red long-wavelength slope is
indicative of an evolved population, although this interpretation is in
contrast to theoretical models of galaxy growth (Prada et al., 2023). A
continued exploration of the stellar properties of JADES sources at $z=7-9$
with red long-wavelength slopes is discussed in Endsley et al. (in prep).
However, until a number of these sources are followed-up with deep
spectroscopy, their nature will remain elusive.

##  6 Conclusions

In this paper, we have assembled a sample of 717 galaxies and candidate
galaxies at $z>8$ selected from the 125 sq. arcmin JWST JADES observations of
GOODS-N and GOODS-S. We combined these data with publicly available medium-
band observations from JEMS and FRESCO, and describe our data reduction and
photometric extraction. Our primary results are listed below:

  * •

Using the template-fitting code EAZY, we calculated photometric redshifts for
the JADES sources, and selected $z>8$ candidates based on source SNR, the
resulting probability of the galaxy being at $z>7$, $P(z>7)$, and the
difference in $\chi^{2}$ between the best-fit at $z>8$ and the fit at $z<7$.
The final sample was visually inspected by seven of the authors, and contains