Abstract
We present a sample of four emission-line galaxies at
z
= 6.11–6.35 that were serendipitously discovered using the commissioning data for the James Webb Space Telescope (JWST)/NIRCam ...wide-field slitless spectroscopy mode. One of them (at
z
= 6.11) has been reported previously, while the others are new discoveries. These sources are selected by the secure detections of both O
iii
λ
5007 and H
α
lines with other fainter lines, which were tentatively detected in some cases (e.g., O
ii
λ
3727, O
iii
λ
4959). In the O
iii
/H
β
–N
ii
/H
α
Baldwin–Phillips–Terlevich diagram, these galaxies occupy the same parameter space as that of
z
∼ 2 star-forming galaxies, indicating that they have been enriched rapidly to subsolar metallicities (∼0.4
Z
⊙
), similar to galaxies with comparable stellar masses at much lower redshifts. The detection of strong H
α
lines suggests a higher ionizing photon production efficiency within galaxies in the early universe. We find brightening of the O
iii
λ
5007 line-luminosity function (LF) from
z
= 3 to 6, and weak or no redshift evolution of the H
α
line LF from
z
= 2 to 6. Both LFs are underpredicted at
z
∼ 6 by a factor of ∼10 in certain cosmological simulations. This further indicates a global Ly
α
photon escape fraction of 7%–10% at
z
∼ 6, which is slightly lower than previous estimates through the comparison of the UV-derived star formation rate density and Ly
α
luminosity density. Our sample recovers
66
−
44
+
128
% of
z
= 6.0–6.6 galaxies in the survey volume with stellar masses greater than 5 × 10
8
M
⊙
, suggesting the ubiquity of strong H
α
and O
iii
line emitters in the Epoch of Reionization, which will be further uncovered in the era of JWST.
Abstract
We present an ALMA-Herschel joint analysis of sources detected by the ALMA Lensing Cluster Survey (ALCS) at 1.15 mm. Herschel/PACS and SPIRE data at 100–500
μ
m are deblended for 180 ALMA ...sources in 33 lensing cluster fields that are detected either securely (141 sources; in our main sample) or tentatively at S/N ≥ 4 with cross-matched HST/Spitzer counterparts, down to a delensed 1.15 mm flux density of ∼0.02 mJy. We performed far-infrared spectral energy distribution modeling and derived the physical properties of dusty star formation for 125 sources (109 independently) that are detected at >2
σ
in at least one Herschel band. A total of 27 secure ALCS sources are not detected in any Herschel bands, including 17 optical/near-IR-dark sources that likely reside at
z
= 4.2 ± 1.2. The 16th, 50th, and 84th percentiles of the redshift distribution are 1.15, 2.08, and 3.59, respectively, for ALCS sources in the main sample, suggesting an increasing fraction of
z
≃ 1 − 2 galaxies among fainter millimeter sources (
f
1150
∼ 0.1 mJy). With a median lensing magnification factor of
μ
=
2.6
−
0.8
+
2.6
, ALCS sources in the main sample exhibit a median intrinsic star formation rate of
94
−
54
+
84
M
⊙
yr
−1
, lower than that of conventional submillimeter galaxies at similar redshifts by a factor of ∼3. Our study suggests weak or no redshift evolution of dust temperature with
L
IR
< 10
12
L
⊙
galaxies within our sample at
z
≃ 0 − 2. At
L
IR
> 10
12
L
⊙
, the dust temperatures show no evolution across
z
≃ 1–4 while being lower than those in the local universe. For the highest-redshift source in our sample (
z
= 6.07), we can rule out an extreme dust temperature (>80 K) that was reported for MACS0416 Y1 at
z
= 8.31.
Abstract
We present a study of the mass–metallicity relation (MZR) of 51 dwarf galaxies (
M
⋆
≈ 10
6.5
–10
9.5
M
⊙
) at
z
= 2–3 from the A2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf ...galaxies are identified and confirmed by deep JWST/NIRISS imaging and slitless grism spectroscopic observations. By taking advantage of the superior performance of JWST and the gravitational lensing effect, we extend the previous MZR relation at
z
= 2–3 to a much lower-mass regime down by ≈2.5 orders of magnitude as compared with previous studies. We find that the MZR has a shallower slope at the low-mass end (
M
⋆
< 10
9
M
⊙
), with a slope turnover point of ≈10
9
M
⊙
. This implies that the dominating feedback processes in dwarf galaxies may be different from that in massive galaxies. From
z
= 3, to
z
= 2, the metallicity of the dwarf galaxies is enhanced by ≈0.09 dex for a given stellar mass, consistent with the mild evolution found in galaxies with higher mass. Furthermore, we confirm the existence of a fundamental metallicity relation (FMR) between the gas-phase metallicity, stellar mass, and star formation rate in dwarf galaxies at
z
= 2–3. Our derived FMR, which has no significant redshift evolution, can be used as a benchmark to understand the origin of the anticorrelation between the star formation rate and metallicity of dwarf galaxies in the high-
z
Universe.
Abstract
We report the multiwavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey ...of well-studied lensing clusters with ALMA, covering an area of 133 arcmin
2
over 33 clusters with a 1.2 mm flux-density limit of ∼60
μ
Jy (1
σ
). Utilizing the archival data of Chandra, we identify three AGNs at
z
= 1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed (
log
N
H
/
cm
−
2
<
23
), while the other shows signs of moderate absorption (
log
N
H
/
cm
−
2
∼
23.5
). We also perform spectral energy distribution modeling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass-accretion rates (intrinsic 0.5–8 keV X-ray luminosities of ∼10
44–45
erg s
−1
) and star formation rates (≳100
M
⊙
yr
−1
). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes in the high-redshift universe.
Abstract The James Webb Space Telescope provides an unprecedented opportunity for unbiased surveys of H α -emitting galaxies at z > 4 with the NIRCam's wide-field slitless spectroscopy (WFSS). In ...this work, we present a census of Ly α escape fraction ( f esc,Ly α ) of 165 star-forming galaxies at z = 4.9–6.3, utilizing their H α emission directly measured from FRESCO NIRCam/WFSS data. We search for Ly α emission of each H α -emitting galaxy in the Very Large Telescope/MUSE data. The overall f esc,Ly α measured by stacking is 0.090 ± 0.006. We find that f esc,Ly α displays a strong dependence on the observed UV slope ( β obs ) and E ( B − V ), such that the bluest galaxies ( β obs ∼ −2.5) have the largest escape fractions ( f esc,Ly α ≈ 0.6), indicative of the crucial role of dust and gas in modulating the escape of Ly α photons. f esc,Ly α is less well related to other parameters, including the UV luminosity and stellar mass, and the variation in f esc,Ly α with them can be explained by their underlying coupling with E ( B − V ) or β obs . Our results suggest a tentative decline in f esc,Ly α at z ≳ 5, implying increasing intergalactic medium attenuation toward higher redshift. Furthermore, the dependence of f esc,Ly α on β obs is proportional to that of the ionizing photon escape fraction ( f esc,LyC ), indicating that the escape of Ly α and ionizing photon may be regulated by similar physical processes. With f esc,Ly α as a proxy to f esc,LyC , we infer that UV-faint ( M UV > −16) galaxies contribute >70% of the total ionizing emissivity at z = 5–6. If these relations hold during the epoch of reionization, UV-faint galaxies can contribute the majority of UV photon budget to reionize the Universe.
Abstract
The dramatic first images with JWST demonstrated its power to provide unprecedented spatial detail for galaxies in the high-redshift universe. Here, we leverage the resolution and depth of ...the JWST Cosmic Evolution Early Release Science Survey data in the Extended Groth Strip to perform pixel-level morphological classifications of galaxies in JWST F150W imaging using the Morpheus deep-learning framework for astronomical image analysis. By cross-referencing with existing photometric redshift catalogs from the Hubble Space Telescope (HST) CANDELS survey, we show that JWST images indicate the emergence of disk morphologies before
z
∼ 2 and with candidates appearing as early as
z
∼ 5. By modeling the light profile of each object and accounting for the JWST point-spread function, we find the high-redshift disk candidates have exponential surface brightness profiles with an average Sérsic index 〈
n
〉 = 1.04 and >90% displaying “disky” profiles (
n
< 2). Comparing with prior Morpheus classifications in CANDELS we find that a plurality of JWST disk galaxy candidates were previously classified as
compact
based on the shallower HST imagery, indicating that the improved optical quality and depth of the JWST helps to reveal disk morphologies that were hiding in the noise. We discuss the implications of these early disk candidates on theories for cosmological disk galaxy formation.
Abstract
Spiral arms serve crucial purposes in star formation and galaxy evolution. In this paper, we report the identification of “A2744-DSG-
z
3,” a dusty, multiarm spiral galaxy at
z
= 3.059 using ...the James Webb Space Telescope (JWST) NIRISS imaging and grism spectroscopy. A2744-DSG-z3 was discovered as a gravitationally lensed submillimeter galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). This is the most distant stellar spiral structure seen thus far, consistent with cosmological simulations that suggest
z
≈ 3 as the epoch when spirals emerge. Thanks to the gravitational lensing and excellent spatial resolution of JWST, the spiral arms are resolved with a spatial resolution of ≈290 pc. Based on spectral energy distribution fitting, the spiral galaxy has a delensed star formation rate of 85 ± 30
M
⊙
yr
−1
, and a stellar mass of ≈10
10.6
M
⊙
, indicating that A2744-DSG-
z
3 is a main-sequence galaxy. After fitting the spiral arms, we find a stellar effective radius (
R
e,star
) of 5.0 ± 1.5 kpc. Combining with ALMA measurements, we find that the effective radii ratio between dust and stars is ≈0.4, similar to those of massive star‐forming galaxies (SFGs) at
z
∼ 2, indicating a compact dusty core in A2744-DSG-z3. Moreover, this galaxy appears to be living in a group environment: including A2744-DSG-z3, at least three galaxies at
z
= 3.05–3.06 are spectroscopically confirmed by JWST/NIRISS and ALMA, residing within a lensing-corrected projected scale of ≈70 kpc. This, along with the asymmetric brightness profile, further suggests that the spiral arms may be triggered by minor-merger events at
z
≳ 3.
Abstract
We present a Spitzer/IRAC survey of
H
-faint (
H
160
≳ 26.4, < 5
σ
) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of ∼648 arcmin
2
(effectively ∼221 arcmin
2
...in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5
μ
m; median CH2 = 22.46 ± 0.11 AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest
H
-faint galaxy at 4.5
μ
m known so far (CH2 = 20.48 ± 0.03 AB mag). We show that the
H
-faint sources in our sample are massive (median
M
star
= 10
10.3±0.3
M
⊙
), star-forming (median star formation rate
=
100
−
40
+
60
M
⊙
yr
−1
), and dust-obscured (
A
V
= 2.6 ± 0.3) galaxies around a median photometric redshift of
z
= 3.9 ± 0.4. The stellar continua of 14
H
-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius (
R
e,circ
; lensing corrected) of 1.9 ± 0.2 kpc and <1.5 kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at
z
∼ 4, indicating that
H
-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in
H
-faint galaxies is related to the compactness of both stellar and dust continua (
R
e,circ
∼ 1 kpc). These
H
-faint galaxies make up
16
−
7
+
13
% of the galaxies in the stellar-mass range of 10
10
− 10
11.2
M
⊙
at
z
= 3 ∼ 5, contributing to
8
−
4
+
8
% of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation.
Abstract We report the discovery of an extreme galaxy overdensity at z = 5.4 in the GOODS-S field using James Webb Space Telescope (JWST)/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam ...wide-field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using Hubble Space Telescope+JWST photometry spanning λ = 0.4–5.0 μ m. These data provide accurate and well-constrained photometric redshifts down to m ≈ 29–30 mag. We subsequently confirmed N = 81 galaxies at 5.2 < z < 5.5 using JWST slitless spectroscopy over λ = 3.9–5.0 μ m through a targeted line search for H α around the best-fit photometric redshift. We verified that N = 42 of these galaxies reside in the field, while N = 39 galaxies reside in a density around ∼10 times that of a random volume. Stellar populations for these galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and exhibited earlier star formation (and thus older stellar populations) when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be 12.6 ≲ log 10 M halo / M ⊙ ≲ 12.8 using an empirical stellar mass to halo mass relation, which is likely an underestimate as a result of incompleteness. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.
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![First Sample of Hα+[O iii]λ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "First Sample of Hα+[O iii]λ5007 Line Emitters at z > 6 Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line-luminosity Functions")
