Abstract
We present the results of a first search for galaxy candidates at
z
∼ 9–15 on deep seven-band NIRCam imaging acquired as part of the GLASS-James Webb Space Telescope (JWST) Early Release ...Science Program on a flanking field of the Frontier Fields cluster A2744. Candidates are selected via two different renditions of the Lyman-break technique, isolating objects at
z
∼ 9–11, and
z
∼ 9–15, respectively, supplemented by photometric redshifts obtained with two independent codes. We find five color-selected candidates at
z
> 9, plus one additional candidate with photometric redshift
z
phot
≥ 9. In particular, we identify two bright candidates at
M
UV
≃ −21 that are unambiguously placed at
z
≃ 10.6 and
z
≃ 12.2, respectively. The total number of galaxies discovered at
z
> 9 is in line with the predictions of a nonevolving luminosity function. The two bright ones at
z
> 10 are unexpected given the survey volume, although cosmic variance and small number statistics limits general conclusions. This first search demonstrates the unique power of JWST to discover galaxies at the high-redshift frontier. The candidates are ideal targets for spectroscopic follow-up in Cycle-2.
We investigate the relation between star formation rate (SFR) and stellar mass (M), i.e., the main sequence (MS) relation of star-forming galaxies, at in the first four Hubble Space Telescope (HST) ...Frontier Fields, on the basis of rest-frame UV observations. Gravitational lensing combined with deep HST observations allows us to extend the analysis of the MS down to at and at higher redshifts, a factor of ∼10 below most previous results. We perform an accurate simulation to take into account the effect of observational uncertainties and correct for the Eddington bias. This step allows us to reliably measure the MS and in particular its slope. While the normalization increases with redshift, we fit an unevolving and approximately linear slope. We nicely extend to lower masses the results of brighter surveys. Thanks to the large dynamic range in mass and by making use of the simulation, we analyzed any possible mass dependence of the dispersion around the MS. We find tentative evidence that the scatter decreases with increasing mass, suggesting a larger variety of star formation histories in low-mass galaxies. This trend agrees with theoretical predictions and is explained as either a consequence of the smaller number of progenitors of low-mass galaxies in a hierarchical scenario and/or of the efficient but intermittent stellar feedback processes in low-mass halos. Finally, we observe an increase in the SFR per unit stellar mass with redshift milder than predicted by theoretical models, implying a still incomplete understanding of the processes responsible for galaxy growth.
ABSTRACT We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity functions at z = 4-8. We use deep Hubble Space Telescope imaging over the Cosmic Assembly ...Near-infrared Deep Extragalactic Legacy Survey/GOODS fields, the Hubble Ultra Deep Field, and the Hubble Frontier Field deep parallel observations near the Abell 2744 and MACS J0416.1-2403 clusters. The combination of these surveys provides an effective volume of 0.6-1.2 × 106 Mpc3 over this epoch, allowing us to perform a robust search for faint 18) and bright (M 21) high-redshift galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 candidate galaxies at 3.5 8.5, with >1000 galaxies at 6-8. We measure both a stepwise luminosity function for candidate galaxies in our redshift samples, and a Schechter function, using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end, our UV luminosity functions agree with previous studies, yet we find a higher abundance of UV-bright candidate galaxies at 6. Our best-fit value of the characteristic magnitude is consistent with −21 at 5, which is different than that inferred based on previous trends at lower redshift, and brighter at ∼2 significance than previous measures at z = 6 and 7. At z = 8, a single power law provides an equally good fit to the UV luminosity function, while at z = 6 and 7 an exponential cutoff at the bright end is moderately preferred. We compare our luminosity functions to semi-analytical models, and find that the lack of evolution in is consistent with models where the impact of dust attenuation on the bright end of the luminosity function decreases at higher redshift, although a decreasing impact of feedback may also be possible. We measure the evolution of the cosmic star-formation rate (SFR) density by integrating our observed luminosity functions to , correcting for dust attenuation, and find that the SFR density declines proportionally to (1 ) at 4, which is consistent with observations at 9. Our observed luminosity functions are consistent with a reionization history that starts at 10, completes at 6, and reaches a midpoint (x 0.5) at 6.7 9.4. Finally, using a constant cumulative number density selection and an empirically derived rising star-formation history, our observations predict that the abundance of bright z = 9 galaxies is likely higher than previous constraints, although consistent with recent estimates of bright 10 galaxies.
ABSTRACT
We measure the size–luminosity relation of photometrically selected galaxies within the redshift range z ∼ 6–9, using galaxies lensed by six foreground Hubble Frontier Fields (HFF) clusters. ...The power afforded by strong gravitational lensing allows us to observe fainter and smaller galaxies than in blank fields. We select our sample of galaxies and obtain their properties, e.g. redshift, magnitude, from the photometrically derived ASTRODEEP catalogues. The intrinsic size is measured with the Lenstruction software, and completeness maps are created as a function of size and luminosity via the GLACiAR2 software. We perform a Bayesian analysis to estimate the intrinsic and incompleteness-corrected size–luminosity distribution, with parametrization re ∝ Lβ. We find slopes of $\beta =0.50^{+0.07}_{-0.07}$ at z ∼ 6 − 7 and $\beta =0.67^{+0.14}_{-0.15}$ at z ∼ 8.5, adopting the Bradac lens model. Our inferred slopes are consistent with other independent determinations of the size–luminosity relation from the HFF data set and steeper than that obtained from the bright galaxies in blank fields. We also investigate the systematic uncertainties associated with the choice of lens models, finding that the slopes of size–luminosity relations derived from different models are mutually consistent, i.e. modelling errors are not a significant source of discrepancy between the size–luminosity relation of blank and lensed fields.
Abstract
We report the detection of a high density of redshift
z
≈ 10 galaxies behind the foreground cluster A2744, selected from imaging data obtained recently with NIRCam on board JWST by three ...programs—GLASS-JWST, UNCOVER, and DDT#2756. To ensure robust estimates of the lensing magnification
μ
, we use an improved version of our model that exploits the first epoch of NIRCam images and newly obtained MUSE spectra and avoids regions with
μ
> 5 where the uncertainty may be higher. We detect seven bright
z
≈ 10 galaxies with demagnified rest frame −22 ≲
M
UV
≲ −19 mag, over an area of ∼37 arcmin
2
. Taking into account photometric incompleteness and the effects of lensing on luminosity and cosmological volume, we find that the density of
z
≈ 10 galaxies in the field is about 10× (3×) larger than the average at
M
UV
≈ −21 ( −20) mag reported so far. The density is even higher when considering only the GLASS-JWST data, which are the deepest and the least affected by magnification and incompleteness. The GLASS-JWST field contains five out of seven galaxies, distributed along an apparent filamentary structure of 2 Mpc in projected length, and includes a close pair of candidates with
M
UV
< −20 mag having a projected separation of only 16 kpc. These findings suggest the presence of a
z
≈ 10 overdensity in the field. In addition to providing excellent targets for efficient spectroscopic follow-up observations, our study confirms the high density of bright galaxies observed in early JWST observations but calls for multiple surveys along independent lines of sight to achieve an unbiased estimate of their average density and a first estimate of their clustering.
Abstract
We present the spectroscopic confirmation of a protocluster at
z
= 7.88 behind the galaxy cluster Abell 2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a ...projected radius of 60 kpc. Although the galaxies reside in an overdensity around ≳20× greater than a random volume, they do not show strong Ly
α
emission. We place 2
σ
upper limits on the rest-frame equivalent width <16–28 Å. Based on the tight upper limits to the Ly
α
emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be
x
HI
> 0.45 (68% C
i
). Using an empirical
M
UV
–
M
halo
relation for individual galaxies, we estimate that the total halo mass of the system is ≳4 × 10
11
M
⊙
. Likewise, the line-of-sight velocity dispersion is estimated to be 1100 ± 200 km s
−1
. Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be ∼2 × 10
15
M
⊙
, comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at <20 hr total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.
Abstract
Despite significant efforts in recent years, the physical processes responsible for the formation of passive galaxies through cosmic time remain unclear. The shape and evolution of the ...stellar mass function (SMF) give an insight into these mechanisms. Taking advantage of the CANDELS and the deep Hubble Frontier Fields (HFF) programs, we estimated the SMF of total, star-forming, and passive galaxies from
z
= 0.25 to
z
= 2.75 to unprecedented depth and we focus on the latter population. The density of passive galaxies underwent a significant evolution over the last 11 Gyr. They account for 60% of the total mass in the nearby universe against ∼20% observed at
z
∼ 2.5. The inclusion of the HFF program allows us to detect, for the first time at
z
> 1.5, the characteristic upturn in the SMF of passive galaxies at low masses, usually associated with environmental quenching. We observe two separate populations of passive galaxies evolving on different timescales: roughly half of the high-mass systems were already quenched at high redshift, while low-mass passive galaxies are gradually building up over the redshift range probed. In the framework of environmental quenching at low masses, we interpret this finding as evidence of an increasing role of the environment in the buildup of passive galaxies as a function of time. Finally, we compared our findings with a set of theoretical predictions. Despite good agreement in some redshift and mass intervals, none of the models are able to fully reproduce the observations. This calls for further investigation into the involved physical mechanisms, both theoretically and observationally, especially with the brand-new JWST data.
Abstract
We present the reduced images and multiwavelength catalog of the first JWST NIRCam extragalactic observations from the GLASS Early Release Science Program, obtained as coordinated parallels ...of the NIRISS observations of the Abell 2744 cluster. Images in seven bands (F090W, F115W, F150W, F200W, F277W, F356W, and F444W) have been reduced using an augmented version of the official JWST pipeline; we discuss the procedures adopted to remove or mitigate defects in the raw images. We obtain a multiband catalog by means of forced aperture photometry on point-spread function (PSF)-matched images at the position of F444W-detected sources. The catalog is intended to enable early scientific investigations, and it is optimized for faint galaxies; it contains 6368 sources, with limiting magnitude 29.7 at 5
σ
in F444W. We release both images and catalog in order to allow the community to become familiar with the JWST NIRCam data and evaluate their merit and limitations given the current level of knowledge of the instrument.
Abstract
Ly
α
emission from galaxies can be used to trace neutral hydrogen in the epoch of reionization, however, there is a degeneracy between the attenuation of Ly
α
in the intergalactic medium ...(IGM) and the line profile emitted by the galaxy. Large shifts of Ly
α
redward of systemic due to scattering in the interstellar medium can boost Ly
α
transmission in the IGM during reionization. The relationship between the Ly
α
velocity offset from systemic and other galaxy properties is not well established at high redshift or low luminosities, due to the difficulty of observing emission lines which trace the systemic redshift. Rest-frame optical spectroscopy with JWST/NIRSpec has opened a new window into understanding Ly
α
at
z
> 3. We present a sample of 12 UV-faint galaxies (−20 ≲
M
UV
≲ −16) at 3 ≲
z
≲ 6, with Ly
α
velocity offsets, Δ
v
Ly
α
, measured from the Very Large Telescope/MUSE and JWST/NIRSpec from the GLASS-JWST Early Release Program. We find a median Δ
v
Ly
α
of 205 km s
−1
and standard deviation of 75 km s
−1
, compared to 320 and 170 km s
−1
, respectively, for
M
UV
< −20 galaxies in the literature. Our new sample demonstrates the previously observed trend of decreasing Ly
α
velocity offset with decreasing UV luminosity and optical line velocity dispersion, which extends to
M
UV
≳ −20, consistent with a picture where the Ly
α
profile is shaped by gas close to the systemic redshift. Our results imply that during reionization Ly
α
from UV-faint galaxies will be preferentially attenuated, but that detecting Ly
α
with low Δ
v
Ly
α
can be an indicator of large ionized bubbles.
Abstract
We present images and a multiwavelength photometric catalog based on all of the JWST NIRCam observations obtained to date in the region of the Abell 2744 galaxy cluster. These data come from ...three different programs, namely, the GLASS-JWST Early Release Science Program, UNCOVER, and the Director’s Discretionary Time program 2756. The observed area in the NIRCam wide-band filters—covering the central and extended regions of the cluster, as well as new parallel fields—is 46.5 arcmin
2
in total. All images in eight bands (F090W, F115W, F150W, F200W, F277W, F356W, F410M, and F444W) have been reduced adopting the latest calibration and reference files available. Data reduction has been performed using an augmented version of the official JWST pipeline, with improvements aimed at removing or mitigating defects in the raw images and improving the background subtraction and photometric accuracy. We obtain an F444W-detected multiband catalog, including all NIRCam and available Hubble Space Telescope data, adopting forced-aperture photometry on point-spread-function-matched images. The catalog is intended to enable early scientific investigations and is optimized for the study of faint galaxies; it contains 24,389 sources, with a 5
σ
limiting magnitude in the F444W band ranging from 28.5 AB to 30.5 AB, as a result of the varying exposure times of the surveys that observed the field. We publicly release the reduced NIRCam images, associated multiwavelength catalog, and the code adopted for 1/
f
noise removal with the aim of aiding users in familiarizing themselves with JWST NIRCam data and identifying suitable targets for follow-up observations.
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