Abstract
We make use of sensitive (9.3
μ
Jy beam
−1
rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field ...(ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range
z
= 1.5–10 (to ∼7–28
M
⊙
yr
−1
at 4
σ
over the entire range). We find that the fraction of ALMA-detected galaxies in our
z
= 1.5–10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 10
9.0
M
⊙
to
% at >10
10
M
⊙
. Moreover, on stacking all 1253 low-mass (<10
9.25
M
⊙
) galaxies over the ASPECS footprint, we find a mean continuum flux of −0.1 ± 0.4
μ
Jy beam
−1
, implying a hard upper limit on the obscured star formation rate of <0.6
M
⊙
yr
−1
(4
σ
) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies (
L
IR
/
L
UV
) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at >
and an SMC-like relation at lower masses. Using stellar mass and
β
measurements for
z
∼ 2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between
β
and stellar mass and then use this correlation to show that our IRX–
β
and IRX–stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of
β
and stellar mass. Finally, we present updated estimates of star formation rate density determinations at
z
> 3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at
z
> 2.
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 explore star formation histories (SFHs) of galaxies based on the evolution of the star formation rate stellar mass relation (SFR-M). Using data from the FourStar Galaxy Evolution Survey (ZFOURGE) ...in combination with far-IR imaging from the Spitzer and Herschel observatories we measure the SFR-M relation at 0.5 < z <. Similar to recent works we find that the average infrared spectral energy distributions of galaxies are roughly consistent with a single infrared template across a broad range of redshifts and stellar masses, with evidence for only weak deviations. We find that these two estimates are in broad qualitative agreement, but that there is room for improvement at a more detailed level. At early times the SFHs suggest mass growth rates that are as much as 10 x higher than inferred from the SMF. However, at later times the SFHs under-predict the inferred evolution, as is expected in the case of additional growth due to mergers.
ABSTRACT
Cosmic dust is an essential component shaping both the evolution of galaxies and their observational signatures. How quickly dust builds up in the early Universe remains an open question ...that requires deep observations at (sub-)millimetre wavelengths to resolve. Here, we use Atacama Large Millimeter Array observations of 45 galaxies from the Reionization Era Bright Emission Line Survey (REBELS) and its pilot programs, designed to target C ii and dust emission in UV-selected galaxies at z ∼ 7, to investigate the dust content of high-redshift galaxies through a stacking analysis. We find that the typical fraction of obscured star formation fobs = SFRIR/SFRUV+IR depends on stellar mass, similar to what is observed at lower redshift, and ranges from fobs ≈ 0.3 − 0.6 for galaxies with log10(M⋆/M⊙) = 9.4–10.4. We further adopt the z ∼ 7 stellar mass function from the literature to extract the obscured cosmic star formation rate density (SFRD) from the REBELS survey. Our results suggest only a modest decrease in the SFRD between 3 ≲ z ≲ 7, with dust-obscured star formation still contributing ${\sim}30{{\ \rm per\ cent}}$ at z ∼ 7. While we extensively discuss potential caveats, our analysis highlights the continued importance of dust-obscured star formation even well into the epoch of reionization.
ABSTRACT
The JWST has discovered a surprising abundance of bright galaxy candidates in the very early universe (≤500 Myr after the Big Bang), calling into question current galaxy formation models. ...Spectroscopy is needed to confirm the primeval nature of these candidates, as well as to understand how the first galaxies form stars and grow. Here we present deep spectroscopic and continuum ALMA observations towards GHZ2/GLASS-z12, one of the brightest and most robust candidates at z > 10, identified in the GLASS-JWST Early Release Science Program. We detect a 5.8σ line, offset 0${_{.}^{\prime\prime}}$5 from the JWST position of GHZ2/GLASS-z12, that associating it with the O iii 88 $\mu {\rm m}$ transition, implies a spectroscopic redshift of z = 12.117 ± 0.001. We verify the detection using extensive statistical tests. The oxygen line luminosity places GHZ2/GLASS-z12 above the O iii-SFR relation for metal-poor galaxies, implying an enhancement of O iii emission in this system while the JWST-observed emission is likely a lower-metallicity region. The lack of dust emission seen by these observations is consistent with the blue UV slope observed by JWST, which suggest little dust attenuation in galaxies at this early epoch. Further observations will unambiguously confirm the redshift and shed light on the origins of the wide and offset line and physical properties of this early galaxy. This work illustrates the synergy between JWST and ALMA, and paves the way for future spectroscopic surveys of z > 10 galaxy candidates.
ABSTRACT We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties ...in rich environments at 1.5 < z < 2.5. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infrared imaging ( ) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013 and 2015, ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over 1.57 < z < 2.66 from a combination of nebular emission lines (such as H , N ii, Hβ, O ii, O iii, and S ii) observed at 1-2 m. Based on our medium-band near infrared photometry, we are able to spectrophotometrically flux calibrate our spectra to ∼10% accuracy. ZFIRE reaches 5 emission line flux limits of ∼3 × 10−18 erg s−1 cm−2 with a resolving power of R = 3500 and reaches masses down to ∼109 M . We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to with 0.7% outliers. We measure a slight redshift bias of <0.001, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colors and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically confirmed z ∼ 2 samples across a richer range of environments, here we make available the first public release of the data for use by the community.7
The ionizing photon production efficiency, ion, is a critical parameter that provides a number of physical constraints to the nature of the early universe, including the contribution of galaxies to ...the timely completion of the reionization of the universe. Here, we use KECK/MOSFIRE and ZFOURGE multiband photometric data to explore the ion of a population of galaxies at z ∼ 2 with . Our 130 H detections show a median of 24.8 0.5 when dust corrected using a Calzetti et al. dust prescription. Our values are typical of mass/magnitude selected ion values observed in the z ∼ 2 universe. Using BPASSv2.2.1 and Starburst99 stellar population models with simple parametric star formation histories (SFH), we find that even with models that account for effects of stellar evolution with binaries/stellar rotation, model galaxies at have low H equivalent widths (EWs) and redder colors compared to our z ∼ 2 observed sample. We find that introducing starbursts to the SFHs resolve the tension with the models; however, due to the rapid time evolution of ion, H EWs, and rest-frame optical colors, our Monte Carlo simulations of starbursts show that random distributions of starbursts in evolutionary time of galaxies are unlikely to explain the observed distribution. Thus, either our observed sample is specially selected based on their past SFH, or stellar models require additional mechanisms to reproduce the observed high UV luminosity of galaxies for a given production rate of hydrogen ionizing photons.
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 is possibly the best indirect diagnostic of Lyman continuum (LyC) escape since the conditions that favor the escape of Ly
α
photons are often the same that allow for the escape ...of LyC photons. In this work, we present the rest-frame UV–optical spectral characteristics of 11 Ly
α
emitting galaxies at 3 <
z
< 6—the redshift range that optimizes between intergalactic medium attenuation effects and temporal proximity to the epoch of reionization. From a combined analysis of JWST/NIRSpec and MUSE data, we present the Ly
α
escape fraction and study its correlation with other physical properties of galaxies that might facilitate Ly
α
escape. We find that our galaxies have low masses (80% of the sample with
log
10
M
⋆
<
9.5
M
⊙
), compact sizes (median
R
e
∼ 0.7 kpc), low dust content, moderate O
iii
/O
ii
flux ratios (mean ∼ 6.8 ± 1.2), and moderate Ly
α
escape fractions (mean
f
esc
Ly
α
∼
0.11). Our sample shows characteristics that are broadly consistent with low-redshift galaxies with Ly
α
emission, which are termed as “analogs” of the high-redshift population. We predict the LyC escape fraction in our sample to be low (0.03–0.07), although larger samples in the postreionization epoch are needed to confirm these trends.
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.
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