25 research outputs found
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: 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
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
Self-consistent Combined HST, K -band, and Spitzer Photometric Catalogs of the BUFFALO Survey Fields
This article presents new astronomical source catalogs using data from the BUFFALO Survey. These catalogs contain detailed information for over 100,000 astronomical sources in the six BUFFALO clusters: A370, A2744, AS1063, MACS 0416, MACS 0717, and MACS 1149 spanning a total of 240 arcmin2. The catalogs include positions and forced photometry measurements of these objects in the F275W, F336W, F435W, F606W, F814W, F105W, F125W, F140W, and F160W HST bands, Keck-NIRC2/VLT-HAWKI Ks band, and IRAC Channel 1 and 2 bands. Additionally, we include photometry measurements in the F475W, F625W, and F110W bands for A370. This catalog also includes photometric redshift estimates computed via template fitting using LePhare. When comparing to a spectroscopic reference, we obtain an outlier fraction of 8.6% and scatter, normalized median absolute deviation, of 0.059. The catalogs are publicly available for their use by the community (https://archive.stsci.edu/hlsp/buffalo/)
UNCOVER: A NIRSpec Identification of a Broad-line AGN at z = 8.50
Deep observations with the James Webb Space Telescope (JWST) have revealed an emerging population of red pointlike 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 z = 8.50 displaying a clear broad-line component as inferred from the Hβ line with FWHM = 3439 ± 413 km s−1, 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 a black hole mass of
and a bolometric luminosity of Lbol ∼ 6.6 × 1045 erg s−1. These values imply that our object is accreting at ∼40% 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 , which would lead to an unprecedented ratio of black hole to host mass of at least ∼30%. This is orders of magnitude higher compared to the local QSOs but consistent with recent AGN studies at high redshift with JWST. This finding suggests that a nonnegligible 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-z faint AGN, future NIRSpec observations of larger samples will allow us to further investigate galaxy–black hole coevolution in the early Universe
UNCOVER: Candidate Red Active Galactic Nuclei at 3<z<7 with JWST and ALMA
The James Webb Space Telescope (JWST) is revolutionizing our knowledge of
galaxies and their actively accreting black holes. Using the JWST Cycle 1
Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of
Reionization (UNCOVER) in the lensing field Abell 2744, we report the
identification of a sample of little red dots at that
likely contain highly-reddened accreting supermassive black holes. Using a
NIRCam-only selection to F444W mag, we find 26 sources over the
arcmin field that are blue in F115WF200W (or for ), red in F200WF444W =
(), and are dominated by a point-source like
central component. Of the 20 sources with deep ALMA 1.2-mm coverage, none are
detected individually or in a stack. For the majority of the sample, SED fits
to the JWST+ALMA observations prefer models with hot dust rather than obscured
star-formation to reproduce the red NIRCam colors and ALMA 1.2-mm
non-detections. While compact dusty star formation can not be ruled out, the
combination of extremely small sizes ( pc after
correction for magnification), red rest-frame optical slopes, and hot dust can
by explained by reddened broad-line active galactic nuclei (AGNs). Our targets
have faint mag but inferred
bolometric luminosities of erg/s, reflecting
their obscured nature. If the candidates are confirmed as AGNs with upcoming
UNCOVER spectroscopy, then we have found an abundant population of reddened
luminous AGN that are at least ten times more numerous than UV-luminous AGN at
the same intrinsic bolometric luminosity.Comment: submitted to 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
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