We present a large spectroscopic campaign with Keck/Multi-Object Spectrometer for InfraRed Exploration (MOSFIRE) targeting Ly emission (Ly ) from intrinsically faint Lyman-break galaxies (LBGs) ...behind 12 efficient galaxy cluster lenses. Gravitational lensing allows us to probe the more abundant faint galaxy population to sensitive Ly equivalent-width limits. During the campaign, we targeted 70 LBG candidates with the MOSFIRE Y band, selected photometrically to cover Ly over the range 7 < z < 8.2. We detect signal-to-noise ratio > 5 emission lines in two of these galaxies and find that they are likely Ly at z = 7.148 0.001 and z = 7.161 0.001. We present new lens models for four of the galaxy clusters, using our previously published lens models for the remaining clusters to determine the magnification factors for the source galaxies. Using a Bayesian framework that employs large-scale reionization simulations of the intergalactic medium (IGM) as well as realistic properties of the interstellar medium and circumgalactic medium, we infer the volume-averaged neutral hydrogen fraction, , in the IGM during reionization to be at z = 7.6 0.6. Our result is consistent with a late and rapid reionization scenario inferred by Planck.
Abstract
The GLASS-JWST Early Release Science (hereafter GLASS-JWST-ERS) Program will obtain and make publicly available the deepest extragalactic data of the ERS campaign. It is primarily designed ...to address two key science questions, namely, “what sources ionized the universe and when?” and “how do baryons cycle through galaxies?”, while also enabling a broad variety of first look scientific investigations. In primary mode, it will obtain NIRISS and NIRSpec spectroscopy of galaxies lensed by the foreground Hubble Frontier Field cluster, Abell 2744. In parallel, it will use NIRCam to observe two fields that are offset from the cluster center, where lensing magnification is negligible, and which can thus be effectively considered blank fields. In order to prepare the community for access to this unprecedented data, we describe the scientific rationale, the survey design (including target selection and observational setups), and present pre-commissioning estimates of the expected sensitivity. In addition, we describe the planned public releases of high-level data products, for use by the wider astronomical community.
We study cosmic variance in deep high-redshift surveys and its influence on the determination of the luminosity function for high-redshift galaxies. For several survey geometries relevant for Hubble ...Space Telescope (HST) and James Webb Space Telescope (JWST) instruments, we characterize the distribution of the galaxy number counts. This is obtained by means of analytic estimates via the two-point correlation function in extended Press-Schechter theory, as well as by using synthetic catalogs extracted from N-body cosmological simulations of structure formation. We adopt a simple luminosity-dark halo mass relation to investigate the effects of environment on the fitting of the luminosity function. We show that in addition to variations of the normalization of the luminosity function, a steepening of its slope is also expected in underdense fields, similar to what is observed within voids in the local universe. Therefore, to avoid introducing artificial biases, caution must be taken when attempting to correct for field underdensity, such as in the case of the HST UDF i- dropout sample, which exhibits a deficit of bright counts with respect to the average counts in GOODS. A public version of the cosmic variance calculator based on the two-point correlation function integration is available on the Web at STScI.
The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function ...(LF) from z ~ 10 to z ~ 4. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z ~ 4, z ~ 5, z ~ 6, z ~ 7, z ~ 7, and z ~ 10, respectively, from the ~1000 arcmin super(2) area covered by these data sets. This sample of >10,000 galaxy candidates at z > or =, slanted 4 is by far the largest assembled to date with HST. The selection of z ~ 4-8 candidates over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are at z > or =, slanted 7. Our new LF determinations at z ~ 4 and z ~ 5 span a 6 mag baseline and reach to -16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of >L* galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4sigma significance for a steeper faint-end slope of the UV LF at z > 4, with alpha evolving from alpha = -1.64 + or - 0.04 at z ~ 4 to alpha = -2.06 + or - 0.13 at z ~ 7 (and alpha = -2.02 + or - 0.23 at z ~ 8), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M* from z ~ 7 to z ~ 4; the observed evolution in the LF is now largely represented by changes in phi*. No evidence for a non-Schechter-like form to the z ~ 4-8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio (is proportional to(1 + z) super(-1.5)) of halos provides a good representation of the observed evolution.
We present a full data analysis of the pure-parallel Hubble Space Telescope (HST) imaging observations in the Brightest of Reionizing Galaxies Survey (BoRGz9) in Cycle 22. The medium-deep exposures ...with five HST/WFC3IR+UVIS filter bands from 79 independent sightlines (∼370 arcmin2) provide the least biased determination of number density for z 9 bright galaxies against cosmic variance. After a strict two-step selection for candidate galaxies, including dropout color and photometric redshift analyses, and revision of previous BoRG candidates, we identify one source at z ∼ 10 and two sources at z ∼ 9. The z ∼ 10 candidate shows evidence of line-of-sight lens magnification ( ∼ 1.5), yet it appears surprisingly luminous ( mag), making it one of the brightest candidates at known (∼0.3 mag brighter than the z = 8.68 galaxy EGSY8p7, spectroscopically confirmed by Zitrin and collaborators). For z ∼ 9 candidates, we include previous data points at fainter magnitudes and find that the data are well fitted by a Schechter luminosity function with , mag, and Mpc−3 mag−1, for the first time without fixing any parameters. The inferred cosmic star formation rate density is consistent with unaccelerated evolution from lower redshift.
ABSTRACT
The deep, wide-area (∼800–900 arcmin
2
) near-infrared/WFC3/IR +
Spitzer
/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of ...high-redshift UV luminosity functions. However, the lack of
Hubble Space Telescope
(
HST
) 1.05
μ
m observations over the CANDELS fields has made it difficult to identify
z
∼ 9–10 sources robustly, since such data are needed to confirm the presence of an abrupt Lyman break at 1.2
μ
m. Here, we report on the successful identification of many such
z
∼ 9–10 sources from a new
HST
program (z9-CANDELS) that targets the highest-probability
z
∼ 9–10 galaxy candidates with observations at 1.05
μ
m, to search for a robust Lyman-break at 1.2
μ
m. The potential
z
∼ 9–10 candidates were preselected from the full
HST
,
Spitzer
/IRAC S-CANDELS observations, and the deepest-available ground-based optical+near-infrared observations (CFHTLS-DEEP+HUGS+UltraVISTA+ZFOURGE). We identified 15 credible
z
∼ 9–10 galaxies over the CANDELS fields. Nine of these galaxies lie at
z
∼ 9 and five are new identifications. Our targeted follow-up strategy has proven to be very efficient in making use of scarce
HST
time to secure a reliable sample of
z
∼ 9–10 galaxies. Through extensive simulations, we replicate the selection process for our sample (both the preselection and follow-up) and use it to improve current estimates for the volume density of bright
z
∼ 9 and
z
∼ 10 galaxies. The volume densities we find are 5
and
lower, respectively, than those found at
z
∼ 8. When compared with the best-fit evolution (i.e.,
) in the UV luminosity densities from
z
∼ 8 to
z
∼ 4 integrated to
(−20 mag), these luminosity densities are
and
lower, respectively, than the extrapolated trends. Our new results are broadly consistent with the “accelerated evolution” scenario at
z
> 8, consistent with that seen in many models.
Abstract
We report the discovery of four galaxy candidates observed 450–600 Myr after the Big Bang with photometric redshifts between
z
∼ 8.3 and 10.2 measured using James Webb Space Telescope (JWST) ...NIRCam imaging of the galaxy cluster WHL0137−08 observed in eight filters spanning 0.8–5.0
μ
m, plus nine Hubble Space Telescope filters spanning 0.4–1.7
μ
m. One candidate is gravitationally lensed with a magnification of
μ
∼ 8, while the other three are located in a nearby NIRCam module with expected magnifications of
μ
≲ 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range
log
M
⋆
/
M
⊙
= 8.3–8.7. All appear young, with mass-weighted ages <240 Myr, low dust content
A
V
< 0.15 mag, and specific star formation rates sSFR ∼0.25–10 Gyr
−1
for most. One
z
∼ 9 candidate is consistent with an age <5 Myr and an sSFR ∼10 Gyr
−1
, as inferred from a strong F444W excess, implying O
iii
+H
β
rest-frame equivalent width ∼2000 Å, although an older
z
∼ 10 object is also allowed. Another
z
∼ 9 candidate is lensed into an arc 2.″4 long with a magnification of
μ
∼ 8. This arc is the most spatially resolved galaxy at
z
∼ 9 known to date, revealing structures ∼30 pc across. Follow-up spectroscopy of WHL0137−08 with JWST/NIRSpec will be useful to spectroscopically confirm these high-redshift galaxy candidates and to study their physical properties in more detail.
The IRAC ultradeep field and IRAC Legacy over GOODS programs are two ultradeep imaging surveys at 3.6 and 4.5 mum with the Spitzer Infrared Array Camera (IRAC). The primary aim is to directly detect ...the infrared light of reionization epoch galaxies at z > 7 and to constrain their stellar populations. The observations cover the Hubble Ultra Deep Field (HUDF), including the two HUDF parallel fields, and the CANDELS/GOODS-South, and are combined with archival data from all previous deep programs into one ultradeep data set. The resulting imaging reaches unprecedented coverage in IRAC 3.6 and 4.5 mum ranging from >50 hr over 150 arcmin super(2), >100 hr over 60 sq arcmin super(2), to ~200 hr over 5-10 arcmin super(2). This paper presents the survey description, data reduction, and public release of reduced mosaics on the same astrometric system as the CANDELS/GOODS-South Wide Field Camera 3 (WFC3) data. To facilitate prior-based WFC3+IRAC photometry, we introduce a new method to create high signal-to-noise PSFs from the IRAC data and reconstruct the complex spatial variation due to survey geometry. The PSF maps are included in the release, as are registered maps of subsets of the data to enable reliability and variability studies. Simulations show that the noise in the ultradeep IRAC images decreases approximately as the square root of integration time over the range 20-200 hr, well below the classical confusion limit, reaching 1sigma point-source sensitivities as faint as 15 nJy (28.5 AB) at 3.6 mum and 18 nJy (28.3 AB) at 4.5 mum. The value of such ultradeep IRAC data is illustrated by direct detections of z = 7-8 galaxies as faint as H sub(AB) = 28.
Abstract
We present the first rest-frame optical size–luminosity relation of galaxies at
z
> 7, using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science ...(GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS campaign. Our sample consists of 19 photometrically selected bright galaxies with
m
F444W
≤ 27.8 at 7 <
z
< 9 and
m
F444W
< 28.2 at
z
∼ 9−15. We measure the size of the galaxies in five bands, from rest-frame optical (∼4800 Å) to the UV (∼1600 Å) based on the Sérsic model, and analyse the size–luminosity relation as a function of wavelength. Remarkably, the data quality of the NIRCam imaging is sufficient to probe the half-light radius
r
e
down to ∼100 pc at
z
> 7. Given the limited sample size and magnitude range, we first fix the slope to that observed for larger samples in rest-frame UV using Hubble Space Telescope samples. The median size
r
0
at the reference luminosity
M
= −21 decreases slightly from rest-frame optical (600 ± 80 pc) to UV (450 ± 130 pc). We then refit the size–luminosity relation allowing the slope to vary. The slope is consistent with
β
∼ 0.2 for all bands except F150W, where we find a marginally steeper slope of
β
= 0.53 ± 0.15. The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger samples, it implies that the UV size–luminosity relation breaks toward the faint end, as suggested by lensing studies.
Abstract
We present the first James Webb Space Telescope/NIRCam-led determination of 7 <
z
< 9 galaxy properties based on broadband imaging from 0.8 to 5
μ
m as part of the GLASS-JWST Early Release ...Science program. This is the deepest data set acquired at these wavelengths to date, with an angular resolution ≲0.″14. We robustly identify 13 galaxies with signal-to-noise ratio ≳ 8 in F444W from 8 arcmin
2
of data at
m
AB
≤ 28 from a combination of dropout and photometric redshift selection. From simulated data modeling, we estimate the dropout sample purity to be ≳90%. We find that the number density of these F444W-selected sources is broadly consistent with expectations from the UV luminosity function determined from Hubble Space Telescope data. We characterize galaxy physical properties using a Bayesian spectral energy distribution fitting method, finding a median stellar mass of 10
8.5
M
⊙
and age 140 Myr, indicating they started ionizing their surroundings at redshift
z
> 9.5. Their star formation main sequence is consistent with predictions from simulations. Lastly, we introduce an analytical framework to constrain main-sequence evolution at
z
> 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. While this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of JWST to unveil unprecedented details of galaxy formation in the first billion years.
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