We present a detailed stellar population analysis of 11 bright (H < 26.6) galaxies at z=9−11 (three spectroscopically confirmed) to constrain the chemical enrichment and growth of stellar mass of ...early galaxies. We use the flexible Bayesian spectral energy distribution (SED) fitting code Prospector with a range of star-formation histories (SFHs), a flexible dust attenuation law and a self-consistent modeling of emission lines. This approach allows us to assess how different priors affect our results, and how well we can break degeneracies between dust attenuation, stellar ages, metallicity and emission lines using data which probe only the rest-frame ultraviolet to optical wavelengths. We measure a median observed ultraviolet spectral slope β= −1.87+0.35−0.43 for relatively massive star-forming galaxies (9<log(M?/M)<10), consistent with no change from z=4 to z=9−10 at these stellar masses, implying rapid enrichment. Our SED-fitting results are consistent with a star-forming main sequence with sub-linear slope (0.7±0.2) and specific star-formation rates of 3−10 Gyr−1. However, the stellar ages and SFHs are less well constrained. Using different SFH priors, we cannot distinguish between median mass-weighted ages of ∼50−150 Myr, which corresponds to 50% formation redshifts of z50∼10−12 atz∼9 and is of the order of the dynamical timescales of these systems. Importantly, the models with different SFH priors are able to fit the data equally well. We conclude that the current observational data cannot tightly constrain the mass-buildup timescales of these z=9−11 galaxies, with our results consistent with SFHs implying both a shallow and steep increase of the cosmic SFR density with time at z >10
Abstract
We study the spatially resolved stellar populations of 444 galaxies at 0.3 <
z
< 6.0 in two clusters (WHL 0137–08 and MACS 0647+70) and a blank field, combining imaging data from the Hubble ...Space Telescope and JWST to perform spatially resolved spectral energy distribution (SED) modeling using
piXedfit
. The high spatial resolution of the imaging data combined with magnification from gravitational lensing in the cluster fields allows us to resolve a large fraction of our galaxies (109) to subkiloparsec scales. At redshifts around cosmic noon and higher (2.5 ≲
z
≲ 6.0), we find mass-doubling times to be independent of radius, inferred from flat specific star formation rate (sSFR) radial profiles and similarities between the half-mass and half-SFR radii. At lower redshifts (1.5 ≲
z
≲ 2.5), a significant fraction of our star-forming galaxies shows evidence for nuclear starbursts, inferred from a centrally elevated sSFR and a much smaller half-SFR radius compared to the half-mass radius. At later epochs, we find more galaxies suppress star formation in their centers but are still actively forming stars in the disk. Overall, these trends point toward a picture of inside-out galaxy growth consistent with theoretical models and simulations. We also observe a tight relationship between the central mass surface density and global stellar mass with ∼0.38 dex scatter. Our analysis demonstrates the potential of spatially resolved SED analysis with JWST data. Future analysis with larger samples will be able to further explore the assembly of galaxy mass and the growth of their structures.
The origin of the correlations between mass, morphology, quenched fraction, and formation history in galaxies is difficult to define, primarily due to the uncertainties in galaxy star formation ...histories (SFHs). SFHs are better constrained for higher redshift galaxies, observed closer to their formation and quenching epochs. Here we use "nonparametric" SFHs and a nested sampling method to derive constraints on the formation and quenching timescales of quiescent galaxies at . We model deep HST grism spectroscopy and photometry from the CLEAR (CANDELS Ly Emission at Reionization) survey. The galaxy formation redshifts, z50 (defined as the point where they had formed 50% of their stellar mass) range from (shortly prior to the observed epoch) up to . We find that early formation redshifts are correlated with high stellar-mass surface densities, , where 1 is the stellar mass within 1 pkpc (proper kpc). Quiescent galaxies with the highest stellar-mass surface density, , show a minimum formation redshift: all such objects in our sample have . Quiescent galaxies with lower surface density, , show a range of formation epochs ( ), implying these galaxies experienced a range of formation and assembly histories. We argue that the surface density threshold uniquely identifies galaxies that formed in the first few Gyr after the big bang, and we discuss the implications this has for galaxy formation models.
One of the key questions in understanding galaxy formation and evolution is how starbursts affect the assembly of stellar populations in galaxies over time. We define a burst indicator ( ) that ...compares a galaxy's star formation rates (SFRs) on short (∼10 Myr) and long (∼100 Myr) timescales. To estimate , we apply the detailed time-luminosity relationship for H and near-ultraviolet emission to simulated star formation histories (SFHs) from semi-analytic models and the Mufasa hydrodynamical cosmological simulations. The average of is not a good indicator of star formation stochasticity (burstiness); indeed, we show that this average should be close to zero unless the galaxy population has an average SFH that is rising or falling rapidly. Instead, the width of the distribution characterizes the burstiness of a galaxy population's recent star formation. We find this width to be robust to variations in stellar initial mass function and metallicity. We apply realistic noise and selection effects to the models to generate mock Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) galaxy catalogs and compare these catalogs with 3D-HST observations of 956 galaxies at 0.65 < z < 1.5 detected in H . Measurements of are unaffected by dust measurement errors under the assumption that E(B − V)stars = 0.44 E(B − V)gas (i.e., Qsg = 0.44). However, setting removes an unexpected dependence of the average value of upon dust attenuation and stellar mass in the 3D-HST sample while also resolving disagreements in the distribution of SFRs. However, even varying the dust law cannot resolve all discrepancies between the simulated and the observed galaxies.
We present Keck/MOSFIRE H-band spectroscopy targeting C iii λ1907, 1909 in a z = 7.5056 galaxy previously identified via Ly emission. We detect strong line emission at with a line flux of (2.63 0.52) ...× 10−18 erg s−1 cm−2. We tentatively identify this line as C iii λ1907, but we are unable to detect C iii λ1909 owing to sky emission at the expected location. This gives a galaxy systemic redshift, , with a velocity offset to Ly of = 88 27 km s−1. The ratio of combined C iii/Ly is 0.30-0.45, one of the highest values measured for any z > 2 galaxy. We do not detect Si iii λλ1883, 1892, and place an upper limit on Si iii/C iii < 0.35 (2 ). Comparing our results to photoionization models, the C iii equivalent width (WC iii = 16.23 2.32 ), low Si iii/C iii ratio, and high implied O iii equivalent width (from the Spitzer/IRAC 3.6-4.5 0.8 mag color) require subsolar metallicities (Z 0.1-0.2 Z ) and a high ionization parameter, log U −1.5. These results favor models that produce higher ionization, such as the bpass models for the photospheres of high-mass stars, and that include both binary stellar populations and/or an IMF that extends to 300 M . The combined C iii equivalent width and 3.6-4.5 color are more consistent with ionization from young stars than active galactic nuclei (AGNs); however, we cannot rule out ionization from a combination of an AGN and young stars. We make predictions for James Webb Space Telescope spectroscopy using these different models, which will ultimately test the nature of the ionizing radiation in this source.
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.
Abstract
We report on the gas-phase metallicity gradients of a sample of 238 star-forming galaxies at 0.6 <
z
< 2.6, measured through deep near-infrared Hubble Space Telescope slitless spectroscopy. ...The observations include 12 orbit depth Hubble/WFC3 G102 grism spectra taken as a part of the CANDELS Ly
α
Emission at Reionization (CLEAR) survey, and archival WFC3 G102+G141 grism spectra overlapping the CLEAR footprint. The majority of galaxies in this sample are consistent with having a zero or slightly positive metallicity gradient (
dZ
/
dR
≥ 0, i.e., increasing with radius) across the full mass range probed (8.5 < log
M
*
/
M
⊙
< 10.5). We measure the intrinsic population scatter of the metallicity gradients, and show that it increases with decreasing stellar mass—consistent with previous reports in the literature, but confirmed here with a much larger sample. To understand the physical mechanisms governing this scatter, we search for correlations between the observed gradient and various stellar population properties at fixed mass. However, we find no evidence for a correlation with the galaxy properties we consider—including star formation rates, sizes, star formation rate surface densities, and star formation rates per gravitational potential energy. We use the observed weakness of these correlations to provide material constraints for predicted intrinsic correlations from theoretical models.
Abstract
We analyze a sample of 25 Ne
v
(
λ
3426) emission-line galaxies at 1.4 <
z
< 2.3 using Hubble Space Telescope/Wide Field Camera 3 G102 and G141 grism observations from the CANDELS Ly
α
...Emission at Reionization (CLEAR) survey. Ne
v
emission probes extremely energetic photoionization (creation potential of 97.11 eV) and is often attributed to energetic radiation from active galactic nuclei (AGNs), shocks from supernovae, or an otherwise very hard ionizing spectrum from the stellar continuum. In this work, we use Ne
v
in conjunction with other rest-frame UV/optical emission lines (O
ii
λ
λ
3726, 3729, Ne
iii
λ
3869, H
β
, O
iii
λ
λ
4959, 5007, H
α
+N
ii
λ
λ
6548, 6583, S
ii
λ
λ
6716, 6731), deep (2–7 Ms) X-ray observations (from Chandra), and mid-infrared imaging (from Spitzer) to study the origin of this emission and to place constraints on the nature of the ionizing engine. The majority of the Ne
v
-detected galaxies have properties consistent with ionization from AGNs. However, for our Ne
v
-selected sample, the X-ray luminosities are consistent with local (
z
≲ 0.1) X-ray-selected Seyferts, but the Ne
v
luminosities are more consistent with those from
z
∼ 1 X-ray-selected QSOs. The excess Ne
v
emission requires either reduced hard X-rays or a ∼0.1 keV excess. We discuss possible origins of the apparent Ne
v
excess, which could be related to the “soft (X-ray) excess” observed in some QSOs and Seyferts and/or be a consequence of a complex/anisotropic geometry for the narrow-line region, combined with absorption from a warm, relativistic wind ejected from the accretion disk. We also consider implications for future studies of extreme high-ionization systems in the epoch of reionization (
z
≳ 6) with the James Webb Space Telescope.
Abstract
We report the observation by the Atacama Large Millimeter/submillimeter Array (ALMA) of a
z
≳ 10 galaxy candidate (GHZ1) discovered from the GLASS–JWST Early Release Science Program. Our ...ALMA program aims to detect the O
iii
emission line at the rest-frame frequency 3393.0062 GHz (88.36
μ
m) and far-IR continuum emission with the spectral window setup seamlessly covering a 26.125 GHz frequency range (10.10 <
z
< 11.14). A total of 7 hr of on-source integration was employed, using four frequency settings to cover the full range (1.7 hr per setting), with 0.″7 angular resolution. No line or continuum is clearly detected, with 5
σ
upper limits on the line emission of 0.93 mJy beam
−1
at 25 km s
−1
channel
−1
and on the continuum emission of 30
μ
Jy beam
−1
. We report marginal spectral (at 225 km s
−1
resolution) and continuum features (4.1
σ
and 2.6
σ
peak signal-to-noise ratio, respectively), within 0.″17 from the JWST position of GHZ1. This spectral feature implies
z
= 10.38 and needs to be verified with further observations. Assuming that the best estimate of photometric redshift (
z
=
10.60
−
0.60
+
0.52
) is correct, the model of the galaxy’s broadband spectral energy distribution for the 3
σ
upper limit of the continuum flux from GHZ1 suggests that GHZ1 has a small amount of dust (
M
d
≲ 10
4
M
⊙
) at a high temperature (
T
d
≳ 90 K). The 5
σ
upper limit on the O
iii
88
μ
m
line luminosity and the inferred star formation rate of GHZ1 are consistent with the properties of low-metallicity dwarf galaxies. We also report serendipitous clear detections of six continuum sources at the locations of the JWST galaxy counterparts in the field.
CLEAR: Survey Overview, Data Analysis, and Products Simons, Raymond C.; Papovich, Casey; Momcheva, Ivelina G. ...
The Astrophysical journal. Supplement series,
05/2023, Volume:
266, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
We present an overview of the CANDELS Ly
α
Emission At Reionization (CLEAR) survey. CLEAR is a 130 orbit program of the Hubble Space Telescope using the Wide Field Camera 3 (WFC3) IR G102 ...grism. CLEAR targets 12 pointings divided between the GOODS-N and GOODS-S fields of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). Combined with existing spectroscopic data from other programs, the full CLEAR data set includes spectroscopic imaging of these fields over 0.8–1.7
μ
m. In this paper, we describe the CLEAR survey, the survey strategy, the data acquisition, reduction, processing, and science products and catalogs released alongside this paper. The catalogs include emission line fluxes and redshifts derived from the combination of the photometry and grism spectroscopy for 6048 galaxies, primarily ranging from 0.2 ≲
z
≲ 3. We also provide an overview of CLEAR’s science goals and results. In conjunction with this paper we provide links to electronic versions of the data products, including 1D+2D extracted spectra and emission line maps.
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