176 research outputs found
A lensed protocluster candidate at identified in JWST observations of the galaxy cluster SMACS0723-7327
According to the current paradigm of galaxy formation, the first galaxies
have been likely formed within large dark matter haloes. The fragmentation of
these massive haloes led to the formation of galaxy protoclusters, which are
usually composed of one to a few bright objects, surrounded by numerous fainter
(and less massive) galaxies. These early structures could have played a major
role in reionising the neutral hydrogen within the first billion years of the
Universe; especially, if their number density is significant.Taking advantage
of the unprecedented sensitivity reached by the \textit{James Webb Space
Telescope (JWST)}, galaxy protoclusters can now be identified and studied in
increasing numbers beyond 6. Characterising their contribution to the
UV photon budget could supply new insights into the reionisation process. We
analyse the first JWST dataset behind SMACS0723-7327 to search for
protoclusters at , combining the available spectroscopic and
photometric data. We then compare our findings with semi-analytical models and
simulations. In addition to two bright galaxies (26.5 AB in F277W),
separated by 11\arcsec and spectroscopically confirmed at
, we identify 6 additional galaxies with similar colors in a
\arcsec radius around these (corresponding to R kpc in
the source plane). Using several methods, we estimate the mass of the dark
matter halo of this protocluster, 3.310M
accounting for magnification, consistent with various predictions. The physical
properties of all protocluster members are also in excellent agreement with
what has been previously found at lower redshifts: star-formation main sequence
and protocluster size. This detection adds to just a few protoclusters
currently known in the first billion years of the universe.Comment: 7 pages, 6 Figures. Accepted for publication in A&A Lette
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
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
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
UNCOVER: The growth of the first massive black holes from JWST/NIRSpec -- spectroscopic confirmation of an X-ray luminous AGN at z=10.1
The James Webb Space Telescope is now detecting early black holes (BHs) as
they transition from "seeds" to supermassive BHs. Recently Bogdan et al. (2023)
reported the detection of an X-ray luminous supermassive BH, UHZ-1, with a
photometric redshift at . Such an extreme source at this very high
redshift provides new insights on seeding and growth models for BHs given the
short time available for formation and growth. Harnessing the exquisite
sensitivity of JWST/NIRSpec, here we report the spectroscopic confirmation of
UHZ-1 at . We find that the NIRSpec/Prism spectrum is
typical of recently discovered z~10 galaxies, characterized primarily by
star-formation features. We see no clear evidence of the powerful X-ray source
in the rest-frame UV/optical spectrum, which may suggest heavy obscuration of
the central BH, in line with the Compton-thick column density measured in the
X-rays. We perform a stellar population fit simultaneously to the new NIRSpec
spectroscopy and previously available photometry. The fit yields a stellar mass
estimate for the host galaxy that is significantly better constrained than
prior photometric estimates ().
Given the predicted BH mass (), the resulting
ratio of remains two to three orders of magnitude higher than
local values, thus lending support to the heavy seeding channel for the
formation of supermassive BHs within the first billion years of cosmic
evolution.Comment: 9 pages, 4 figures, submitted to ApJL. Minor text correction
Are JWST/NIRCam color gradients in the lensed z=2.3 dusty star-forming galaxy El Anzuelo due to central dust attenuation or inside-out galaxy growth?
Gradients in the mass-to-light ratio of distant galaxies impede our ability
to characterize their size and compactness. The long-wavelength filters of
's NIRCam offer a significant step forward. For galaxies at Cosmic Noon
(), this regime corresponds to the rest-frame near-infrared, which is
less biased towards young stars and captures emission from the bulk of a
galaxy's stellar population. We present an initial analysis of an extraordinary
lensed dusty star-forming galaxy (DSFG) at behind the
cluster (), named ("The Fishhook") after its partial
Einstein-ring morphology. The FUV-NIR SED suggests an intrinsic star formation
rate of and dust attenuation , in line with other DSFGs on the star-forming main sequence. We develop a
parametric lens model to reconstruct the source-plane structure of dust imaged
by the Atacama Large Millimeter/submillimeter Array, far-UV to optical light
from , and near-IR imaging with 8 filters of /NIRCam, as part of
the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS)
program. The source-plane half-light radius is remarkably consistent from m, despite a clear color gradient where the inferred galaxy center is
redder than the outskirts. We interpret this to be the result of both a
radially-decreasing gradient in attenuation and substantial spatial offsets
between UV- and IR-emitting components. A spatial decomposition of the SED
reveals modestly suppressed star formation in the inner kiloparsec, which
suggests that we are witnessing the early stages of inside-out quenching.Comment: 29 pages, 11 figures, 5 tables. Accepted for publication in Ap
DUALZ: Deep UNCOVER-ALMA Legacy High-Z Survey
We present the survey design and initial results of the ALMA Cycle 9 program
of DUALZ, which aims to establish a joint ALMA and JWST public legacy field
targeting the massive galaxy cluster Abell 2744. DUALZ features a contiguous
ALMA 30-GHz-wide mosaic in Band 6, covering areas of down
to a sensitivity of Jy. Through a blind search, we identified
69 dust continuum sources at S/N with median redshift and
intrinsic 1.2-mm flux of and ~mJy. Of
these, 27 have been spectroscopically confirmed, leveraged by the latest
NIRSpec observations, while photometric redshift estimates are constrained by
the comprehensive HST, NIRCam, and ALMA data for the remaining sources. With
priors, we further identify a [CII]158 m line emitter at
, confirmed by the latest NIRSpec spectroscopy. The NIRCam
counterparts of the 1.2-mm continuum exhibit undisturbed morphologies, denoted
either by disk or spheroid, implying the triggers for the faint mm emission are
less catastrophic than mergers. We have identified 8 HST-dark galaxies
(F150W27mag, F150WF444W2.3) and 2 JWST-dark (F444W30mag) galaxy
candidates among the ALMA continuum sources. The former includes face-on disk
galaxies, hinting that substantial dust obscuration does not always result from
inclination. We also detect a marginal dust emission from an X-ray-detected
galaxy at , suggesting an active co-evolution of the
central black hole and its host. We assess the infrared luminosity function up
to and find it consistent with predictions from galaxy formation
models. To foster diverse scientific outcomes from the community, we publicly
release reduced ALMA mosaic maps, cubes, and the source catalog.Comment: 33 pages, 16 figures, and 5 tables. Submitted to ApJS. The ALMA
products are fully available from here:
https://jwst-uncover.github.io/DR2.html#DUAL
N-Glycosylation of ß4 Integrin Controls the Adhesion and Motility of Keratinocytes
α6ß4 integrin is an essential component of hemidesmosomes and modulates cell migration in wound healing and cancer invasion. To elucidate the role of N-glycosylation on ß4 integrin, we investigated keratinocyte adhesion and migration through the re-expression of wild-type or N-glycosylation-defective ß4 integrin (ΔNß4) in ß4 integrin null keratinocytes. N-glycosylation of ß4 integrin was not essential for the heterodimer formation of ß4 integrin with α6 integrin and its expression on a cell surface, but N-glycosylation was required for integrin-mediated cell adhesion and migration. Concomitantly with the reduction of ß4 integrin in the membrane microdomain, the intracellular signals of Akt and ERK activation were decreased in cells expressing ΔNß4 integrin. Forced cross-linking of ß4 integrin rescued the decreased ERK activation in ΔNß4 integrin-expressing cells to a similar extent in wild-type ß4 integrin-expressing cells. Surprisingly, compared with cells expressing wild-type ß4 integrin, an alternation in N-glycan structures expressed on epidermal growth factor receptor (EGFR), and the induction of a stronger association between EGFR and ß4 integrin were observed in ΔNß4 integrin-expressing cells. These results clearly demonstrated that N-glycosylation on ß4 integrin plays an essential role in keratinocyte cellular function by allowing the appropriate complex formation on cell surfaces
UNCOVER: A NIRSpec Identification of a Broad Line AGN at z = 8.50
Deep observations with JWST have revealed an emerging population of red
point-like sources that could provide a link between the postulated
supermassive black hole seeds and observed quasars. In this work we present a
JWST/NIRSpec spectrum from the JWST Cycle 1 UNCOVER Treasury survey, of a
massive accreting black hole at , displaying a clear broad-line
component as inferred from the H line with FWHM = km
s, typical of the broad line region of an active galactic nucleus (AGN).
The AGN nature of this object is further supported by high ionization, as
inferred from emission lines, and a point-source morphology. We compute the
black hole mass of log, and a bolometric
luminosity of erg s. These values
imply that our object is accreting at of the Eddington limit.
Detailed modeling of the spectral energy distribution in the optical and
near-infrared, together with constraints from ALMA, indicate an upper limit on
the stellar mass of log, which would lead to an
unprecedented ratio of black hole to host mass of at least . This
is orders of magnitude higher compared to the local QSOs, but is consistent
with recent AGN studies at high redshift with JWST. This finding suggests that
a non-negligible fraction of supermassive black holes either started out from
massive seeds and/or grew at a super-Eddington rate at high redshift. Given the
predicted number densities of high- faint AGN, future NIRSpec observations
of larger samples will allow us to further investigate the galaxy-black hole
co-evolution in the early Universe.Comment: 14 pages, 6 figures, 2 tables. Submitted to ApJ
First spectroscopic observations of the galaxies that reionized the Universe
Low-mass galaxies in the early universe are believed to be the building
blocks of present-day galaxies. These fledgling systems likely played a pivotal
role in cosmic reionization, a major phase transition from neutral Hydrogen to
ionized plasma around 600-800 Myr after the Big Bang. However, these galaxies
have eluded comprehensive spectroscopic studies owing to their extreme
faintness. Here we report the first spectroscopic analysis of 8 ultra-faint
galaxies during the epoch of reionization with absolute magnitudes between
M to mag (down to 0.005 ). The
combination of ultra-deep NIRSpec (Near-Infrared Spectrograph) observations and
the strong gravitational lensing boost of Abell~2744 allow us to derive the
first spectroscopic constraints on the prevalence of faint galaxies and their
ionizing properties during the Universe's first billion years. We find that
faint galaxies are prodigious producers of ionizing photons with log(/ Hz erg) =, a factor of 4 larger than canonical
values. This means that the total rate of ionizing photons produced by galaxies
exceeds that needed for reionization, even for modest values of escape fraction
( =5%). These findings provide robust evidence that faint galaxies
were the main drivers of cosmic reionization at .Comment: 29 pages, 7 figures, 2 table
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