66 research outputs found
A variable active galactic nucleus at z = 2.06 triply-imaged by the galaxy cluster MACS J0035.4−2015
Support by grant 2020750 from the United States-
Israel Binational Science Foundation (BSF) and grant 2109066
from the United States National Science Foundation (NSF), and
by the Ministry of Science and Technology, Israel. J.C. acknowl-
edges funding from the ‘FirstGalaxies’ Advanced Grant from the
European Research Council (ERC) under the European Union’s
Horizon 2020 research and innovation program (Grant agreement
No. 789056). E.C.L. acknowledges support of an STFC Webb
Fellowship (ST/W001438/1). K.K. acknowledges the support by
JSPS KAKENHI Grant Number JP17H06130 and the NAOJ ALMA
Scientific Research Grant Number 2017–06B. D.E. acknowledges
support from a Beatriz Galindo senior fellowship (BG20/00224)
from the Spanish Ministry of Science and Innovation, projects
PID2020-114414GB-100 and PID2020-113689GB-I00 financed by
MCIN/AEI/10.13039/501100011033, project P20-00334 financed
by the Junta de Andaluc´ıa, and project A-FQM-510-UGR20 of
the FEDER/Junta de Andaluc´ıa-Consejer´ıa de Transformaci ´on
Econ ´omica, Industria, Conocimiento y Universidades. G.E.M. ac-
knowledges financial support from the Villum Young Investiga-
tor grant 37440 and 13160 and the The Cosmic Dawn Center
(DAWN), funded by the Danish National Research Foundation
under grant No. 140. F.E.B. acknowledges support from ANID-
Chile BASAL CATA FB210003, FONDECYT Regular 1200495 and
1190818, and Millennium Science Initiative Program–ICN12 009.
K.K.K. acknowledges support from the Knut and Alice Wallenberg
Foundation.We report the discovery of a triply imaged active galactic nucleus (AGN), lensed by the galaxy cluster MACS J0035.4−2015 (z d = 0.352). The object is detected in Hubble Space Telescope imaging taken for the RELICS program. It appears to have a quasi-stellar nucleus consistent with a point-source, with a de-magnified radius of re ≲ 100 pc. The object is spectroscopically confirmed to be an AGN at z spec = 2.063 ± 0.005 showing broad rest-frame UV emission lines, and detected in both X-ray observations with Chandra and in ALCS ALMA band 6 (1.2 mm) imaging. It has a relatively faint rest-frame UV luminosity for a quasar-like object, MUV, 1450 = −19.7 ± 0.2. The object adds to just a few quasars or other X-ray sources known to be multiply lensed by a galaxy cluster. Some diffuse emission from the host galaxy is faintly seen around the nucleus, and there is a faint object nearby sharing the same multiple-imaging symmetry and geometric redshift, possibly an interacting galaxy or a star-forming knot in the host. We present an accompanying lens model, calculate the magnifications and time delays, and infer the physical properties of the source. We find the rest-frame UV continuum and emission lines to be dominated by the AGN, and the optical emission to be dominated by the host galaxy of modest stellar mass M✶ ≃ 109.2 M⊙. We also observe some variation in the AGN emission with time, which may suggest that the AGN used to be more active. This object adds a low-redshift counterpart to several relatively faint AGN recently uncovered at high redshifts with HST and JWST.Horizon 2020 Framework Programme
H2020Consejería de Transformación Económica, Industria, Conocimiento y Universidades
13160, 37440Science and Technology Facilities Council ST/W001438/1 STFCEuropean Research Council
ERCFondo Nacional de Desarrollo Científico y Tecnológico
1190818, 1200495, ICN12_009 FONDECYTMinisterio de Ciencia e Innovación
MCIN/AEI/10.13039/501100011033, P20-00334, PID2020-113689GB-I00, PID2020-114414GB-100 MICINNHorizon 2020
789056European Regional Development Fund
ERDFJunta de Andalucía
A-FQM-510-UGR2
Efficient survey design for finding high-redshift galaxies with JWST
Several large JWST blank field observing programs have not yet discovered the
first galaxies expected to form at . This has motivated the
search for more effective survey strategies that will be able to effectively
probe this redshift range. Here, we explore the use of gravitationally lensed
cluster fields, that have historically been the most effective discovery tool
with HST. In this paper, we analyze the effectiveness of the most massive
galaxy clusters that provide the highest median magnification factor within a
single JWST NIRCam module in uncovering this population. The results of
exploiting these lensing clusters to break the barrier are compared
against the results from large area, blank field surveys such as JADES and
CEERS in order to determine the most effective survey strategy for JWST. We
report that the fields containing massive foreground galaxy clusters
specifically chosen to occupy the largest fraction of a single NIRCam module
with high magnification factors in the source plane, whilst containing all
multiple images in the image plane within a single module provide the highest
probability of both probing the regime, as well as
discovering the highest redshift galaxy possible with JWST. We also find that
using multiple massive clusters in exchange for shallower survey depths is a
more time efficient method of probing the regime.Comment: 12 pages, 5 figure
Unscrambling the lensed galaxies in JWST images behind SMACS0723
The first deep field images from the James Webb Space Telescope (JWST) of the
galaxy cluster SMACS~J0723.3-7327 reveal a wealth of new lensed images at
uncharted infrared wavelengths, with unprecedented depth and resolution. Here
we securely identify 14 new sets of multiply imaged galaxies totalling 42
images, adding to the five sets of bright and multiply-imaged galaxies already
known from Hubble Space Telescope data. We find examples of arcs crossing
critical curves, allowing detailed community follow-up, such as JWST
spectroscopy for precise redshift determinations, and measurements of the
chemical abundances and of the detailed internal gas dynamics of very distant,
young galaxies. One such arc contains compact knots of magnification
750, and features a microlensed transient. We also detect an Einstein
cross candidate only visible thanks to JWST's superb resolution. Our parametric
lens model is available at
https://www.dropbox.com/sh/gwup2lvks0jsqe5/AAC2RRSKce0aX-lIFCc9vhBXa?dl=0 , and
will be regularly updated using additional spectroscopic redshifts. The model
reproduces the multiple images to better than an rms of ,
and allows for accurate magnification estimates of high-redshift galaxies. The
intracluster light extends beyond the cluster members, exhibiting large-scale
features that suggest a significant past dynamical disturbance. This work
represents a first taste of the enhanced power JWST will have for
lensing-related science.Comment: Submitted to ApJ. 13 pages, 6 figure
A search for transients in the Reionization Lensing Cluster Survey (RELICS): Three new supernovae
The Reionization Cluster Survey (RELICS) imaged 41 galaxy clusters with the
Hubble Space Telescope (HST), in order to detect lensed and high-redshift
galaxies. Each cluster was imaged to about 26.5 AB mag in three optical and
four near-infrared bands, taken in two distinct visits separated by varying
time intervals. We make use of the multiple near-infrared epochs to search for
transient sources in the cluster fields, with the primary motivation of
building statistics for bright caustic crossing events in gravitational arcs.
Over the whole sample, we do not find any significant ()
caustic crossing events, in line with expectations from semi-analytic
calculations but in contrast to what may be naively expected from previous
detections of some bright events, or from deeper transient surveys that do find
high rates of such events. Nevertheless, we find six prominent supernova (SN)
candidates over the 41 fields: three of them were previously reported and three
are new ones reported here for the first time. Out of the six candidates, four
are likely core-collapse (CC) SNe -- three in cluster galaxies, and among which
only one was known before, and one slightly behind the cluster at
. The other two are likely Ia -- both of them previously known,
one probably in a cluster galaxy, and one behind it at . Our study
supplies empirical bounds for the rate of caustic crossing events in galaxy
cluster fields to typical HST magnitudes, and lays the groundwork for a future
SN rate study.Comment: Accepted for publication in MNRAS. 10 pages, 3 figure
UNCOVERing the extended strong lensing structures of Abell 2744 with the deepest JWST imaging
We present a new parametric lens model for the massive galaxy cluster
Abell~2744 based on the new ultra-deep JWST imaging taken in the framework of
the UNCOVER program. These observations constitute the deepest JWST images of a
lensing cluster to date, adding to the existing deep Hubble Space Telescope
(HST) images and the recent JWST ERS and DDT data taken for this field. The
wide field-of-view of UNCOVER ( arcmin) extends beyond the
cluster's well-studied central core and reveals a spectacular wealth of
prominent lensed features around two massive cluster sub-structures in the
north and north-west, where no multiple images were previously known. The 75
newly uncovered multiple images and candidates of 16 sources allow us, for the
first time, to constrain the lensing properties and total mass distribution
around these extended cluster structures using strong lensing (SL). Our model
yields an effective Einstein radius of for
the main cluster core (for ), enclosing a mass of
M, and
for the newly discovered north-western SL
structure enclosing
M. The northern clump is somewhat less massive with
enclosing
M. We find the
northern sub-structures of Abell~2744 to broadly agree with the findings from
weak lensing (WL) and align with the filamentary structure found by these
previous studies. Our model in particular reveals a large area of high
magnifications between the various cluster structures, which will be paramount
for lensed galaxy studies in the UNCOVER field. The model is made publicly
available to accompany the first UNCOVER data release.Comment: Accepted for publication in MNRAS. Updated to match the published
versio
Quantifying the Effects of Known Unknowns on Inferred High-redshift Galaxy Properties: Burstiness, the IMF, and Nebular Physics
The era of the James Webb Space Telescope ushers stellar populations models
into uncharted territories, particularly at the high-redshift frontier. In a
companion paper, we apply the \texttt{Prospector} Bayesian framework to jointly
infer galaxy redshifts and stellar populations properties from broad-band
photometry as part of the UNCOVER survey. Here we present a comprehensive error
budget in spectral energy distribution (SED) modeling. Using a
sample, we quantify the systematic shifts stemming from various model choices
in inferred stellar mass, star formation rate (SFR), and age. These choices
encompass different timescales for changes in the star formation history (SFH),
non-universal stellar initial mass functions (IMF), and the inclusion of
variable nebular abundances, gas density and ionizing photon budget. We find
that the IMF exerts the strongest influence on the inferred properties: the
systematic uncertainties can be as much as 1 dex, 2--5 times larger than the
formal reported uncertainties in mass and SFR; and importantly, exceed the
scatter seen when using different SED fitting codes. This means that a common
practice in the literature of assessing uncertainties in SED-fitting processes
by comparing multiple codes is substantively underestimating the true
systematic uncertainty. Highly stochastic SFHs change the inferred SFH by much
larger than the formal uncertainties, and introduce dex systematics
in SFR and dex systematics in average age. Finally, employing a
flexible nebular emission model causes dex systematic increase in
mass, comparable to the formal uncertainty. This paper constitutes one of the
initial steps toward a complete uncertainty estimate in SED modeling.Comment: Submitted to ApJ. 18 pages, 8 figures, 2 table
JWST UNCOVER: Discovery of Galaxy Candidates Behind the Lensing Cluster Abell 2744
We present the results of a search for high-redshift () galaxy
candidates in the JWST UNCOVER survey, using deep NIRCam and NIRISS imaging in
7 bands over arcmin and ancillary HST observations. The NIRCam
observations reach a limiting magnitude of AB. The
identification of high candidates relies on a combination of a dropout
selection and photometric redshifts. We find 16 candidates at and 3
candidates at , eight candidates are deemed very robust. Their lensing
amplification ranges from to 11.5. Candidates have a wide range of
(lensing-corrected) luminosities and young ages, with low stellar masses
( log(M/M) ) and low star formation rates
(SFR=0.2-7 M yr), confirming previous findings in early JWST
observations of . A few galaxies at appear to show a clear
Balmer break between the F356W and F444W/F410M bands, which helps constrain
their stellar mass. We estimate blue UV continuum slopes between
and , typical for early galaxies at but not as extreme as the
bluest recently discovered sources. We also find evidence for a rapid
redshift-evolution of the mass-luminosity relation and a redshift-evolution of
the UV continuum slope for a given range of intrinsic magnitude, in line with
theoretical predictions. These findings suggest that deeper JWST observations
are needed to reach the fainter galaxy population at those early epochs, and
follow-up spectroscopy will help better constrain the physical properties and
star formation histories of a larger sample of galaxies.Comment: Submitted to MNRA
UNCOVER: Illuminating the Early Universe -- JWST/NIRSpec Confirmation of Galaxies
Observations of high-redshift galaxies provide a critical direct test to the
theories of early galaxy formation, yet to date, only four have been
spectroscopically confirmed at . Due to strong gravitational lensing over
a wide area, the galaxy cluster field Abell~2744 is ideal for searching for the
earliest galaxies. Here we present JWST/NIRSpec observations of two galaxies: a
robust detection at , and a plausible
candidate at . The galaxies are
discovered in JWST/NIRCam imaging and their distances are inferred with
JWST/NIRSpec spectroscopy, all from the JWST Cycle 1 UNCOVER Treasury survey.
Detailed stellar population modeling using JWST NIRCam and NIRSpec data
corroborates the primeval characteristics of these galaxies: low mass (), young, rapidly-assembling, metal-poor, and star-forming.
Interestingly, both galaxies are spatially resolved, having lensing-corrected
rest-UV effective radii on the order of 300-400 pc, which are notably larger
than other spectroscopically confirmed systems. The observed
dynamic range of size spans over an order of magnitude, implying
a significant scatter in the size-mass relation at early times. Deep into the
epoch of reionization, these discoveries elucidate the emergence of the first
galaxies.Comment: submitted to ApJL; 13 pages, 4 figures, 2 table
High-Redshift Galaxy Candidates at as Revealed by JWST Observations of WHL0137-08
JWST was designed to peer into the distant universe and study galaxies nearer
the beginning of time than previously. Here we report the discovery of 12
galaxy candidates observed 300-600 Myr after the Big Bang with photometric
redshifts between z ~ 8.5-13 measured using JWST NIRCam imaging of the galaxy
cluster WHL0137 observed in 8 filters spanning 0.8-5.0 m, plus 9 HST
filters spanning 0.4-1.7 m. Three of these candidates are gravitationally
lensed by the foreground galaxy cluster and have magnifications of . The remaining nine candidates are located in a second JWST NIRCam module,
centered ~29' from the cluster center, with expected magnifications of <~
1.1. Our sample of high-redshift candidates have observed F200W AB magnitudes
between 25.9 and 28.1 mag and intrinsic F200W AB magnitudes between 26.4 and
29.7 mag ( = -22.5 to -17). We find the stellar masses of these
galaxies are in the range = 8 - 9, and down to 7.5 for
the lensed galaxies. All are young with mass-weighted ages < 100 Myr, low dust
content < 0.15 mag, and high specific star formation rates sSFR ~10-50
Gyr for most. One z ~ 9 candidate is consistent with an age < 5 Myr and
a sSFR ~250 Gyr, as inferred from a strong F444W excess, implying
[OIII]+H-beta rest-frame equivalent width ~2000 Angstrom, although an older and
redder z~ 10 object is also allowed. Another z~9 candidate ID9356 is lensed
into an arc 2.6" long by the effects of strong gravitational lensing (~8),
and has at least two bright knots of unevenly distributed star formation. This
arc is the most spatially-resolved galaxy at z~9 known to date, revealing
structures ~30 pc across. Follow-up spectroscopy of WHL0137 with JWST/NIRSpec
is planned for later this year, which will validate some of these candidates
and study their physical properties in more detail.Comment: submitted to Ap
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