97 research outputs found
CEERS Key Paper. I. An Early Look into the First 500 Myr of Galaxy Formation with JWST
We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z ⌠0.5 to >10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 arcmin 2, to search for candidate galaxies at z > 9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multiband photometry across seven NIRCam broad- and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z ⌠9-16. These objects are compact with a median half-light radius of âŒ0.5 kpc. We present an early estimate of the z ⌠11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M UV ⌠â20 appears to evolve very little from z ⌠9 to 11. We also find that the abundance (surface density [arcmin â2]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z > 10, star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultrahigh-redshift galaxies with which to further explore these conclusions.</p
Delving deep: a population of extremely dusty dwarfs observed by JWST
We take advantage of the NIRCam photometric observations available as part of
the Cosmic Evolution Early Release Science survey (CEERS) to identify and
analyse very red sources in an effort to discover very dusty star forming
galaxies. We select red galaxies as objects with a S/N>3 at 4.4 m and a
S/N<2 in all JWST and HST filters at m, which corresponds to
[F200W]-[F444W]>1.2 considering CEERS depths. This selection is ideal to
identify very dusty (Av>1 mag) galaxies with stellar masses between to
at z<5, more massive dusty galaxies at z=5-18 and
galaxies at z>18 due to the Lyman absorption, independently of their dust
extinction. Our sample of F200W-dropouts contains no strong candidates at
z>6.5, instead it consists almost completely (~81%) of z<2 low-mass galaxies,
with a median stellar mass of . These galaxies show an
exceptional dust extinction with median value of Av=4.9 mag, completely
unexpected given their low stellar mass. The remaining galaxies, which are at
z1), but they are generally more
massive .Comment: 30 pages, 1 table, 19 figures, accepted for publication in A&
JWST NIRCam Photometry: A Study of Globular Clusters Surrounding Bright Elliptical Galaxy VV 191a at z=0.0513
James Webb Space Telescope NIRCam images have revealed 443 globular cluster
(GC) candidates around the elliptical galaxy VV 191a. NIRCam
broadband observations are made at 0.9-4.5 m using filters F090W, F150W,
F356W, and F444W. Using photometry, the data is analyzed to present
color-magnitude diagrams (CMDs) that suggest a fairly uniform population of
GCs. Color histograms show a unimodal color distribution that is well fit by a
single Gaussian, using color to primarily trace the metallicity. The findings
show the sample's globular cluster luminosity function (GCLF) does not reach
the turnover value and is, therefore, more luminous than what is typically
expected, with an absolute AB magnitude, mag, reaching
within nearly one magnitude of the classical turnover value. We attribute this
to the completeness in the sample. Models show that the mass estimate of the
GCs detected tends to be more massive, reaching upward of . However, the results show that current GC models do not quite align
with the data. We find that the models appear to be bluer than the JWST data in
the reddest (F356W-F444W) filters and redder than the data in the bluest
(F090W-F150W) filters and may need to be revised to improve the modeling of
near-IR colors of old, metal-poor stellar populations.Comment: 11 pages, 7 figure
Galaxy morphology from z ~ 6 through the lens of JWST
Context: The James Webb Space Telescope's (JWST's) unprecedented combination of sensitivity, spatial resolution, and infrared coverage has enabled a new era of galaxy morphology exploration across most of cosmic history. Aims: We analyze the near-infrared (NIR ~ 0.8 -1 ÎŒm) rest-frame morphologies of galaxies with log Mâ/Mâ > 9 in the redshift range of 0 < z < 6, compare with previous HST-based results and release the first JWST-based morphological catalog of ~20 000 galaxies in the CEERS survey. Methods: We classified the galaxies in our sample into four main broad classes: spheroid, disk+spheroid, disk, and disturbed, based on imaging with four filters: F150W, F200W, F356W, and F444W. We used convolutional neural networks (CNNs) trained on HST/WFC3 labeled images and domain-adapted to JWST/NIRCam. Results: We find that ~90% and ~75% of galaxies at z < 3 have the same early and late and regular and irregular classification, respectively, in JWST and HST imaging when considering similar wavelengths. For small (large) and faint objects, JWST-based classifications tend to systematically present less bulge-dominated systems (peculiar galaxies) than HST-based ones, but the impact on the reported evolution of morphological fractions is less than ~10%. Using JWST-based morphologies at the same rest-frame wavelength ( ~0.8 -1 ÎŒm), we confirm an increase in peculiar galaxies and a decrease in bulge-dominated galaxies with redshift, as reported in previous HST-based works, suggesting that the stellar mass distribution, in addition to light distribution, is more disturbed in the early Universe. However, we find that undisturbed disk-like systems already dominate the high-mass end of the late-type galaxy population (log Mâ/Mâ > 10.5) at z ~ 5, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies ~1 Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at z > 3, with massive quiescent galaxies (log Mâ/Mâ > 10.5) being predominantly bulge-dominated.</p
CEERS: 7.7 m PAH Star Formation Rate Calibration with JWST MIRI
We test the relationship between UV-derived star formation rates (SFRs) and
the 7.7 m polycyclic aromatic hydrocarbon (PAH) luminosities from the
integrated emission of galaxies at z ~ 0 - 2. We utilize multi-band photometry
covering 0.2 - 160 m from HST, CFHT, JWST, Spitzer, and Herschel for
galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We
perform spectral energy distribution (SED) modeling of these data to measure
dust-corrected far-UV (FUV) luminosities, , and UV-derived SFRs. We
then fit SED models to the JWST/MIRI 7.7 - 21 m CEERS data to derive
rest-frame 7.7 m luminosities, , using the average flux density
in the rest-frame MIRI F770W bandpass. We observe a correlation between
and , where log is proportional to (1.27+/-0.04)
log . diverges from this relation for galaxies at lower
metallicities, lower dust obscuration, and for galaxies dominated by evolved
stellar populations. We derive a "single-wavelength" SFR calibration for
which has a scatter from model estimated SFRs
() of 0.24 dex. We derive a "multi-wavelength"
calibration for the linear combination of the observed FUV luminosity
(uncorrected for dust) and the rest-frame 7.7 m luminosity, which has a
scatter of = 0.21 dex. The relatively small decrease
in suggests this is near the systematic accuracy of the total SFRs
using either calibration. These results demonstrate that the rest-frame 7.7
m emission constrained by JWST/MIRI is a tracer of the SFR for distant
galaxies to this accuracy, provided the galaxies are dominated by
star-formation with moderate-to-high levels of attenuation and metallicity.Comment: 20 pages, 11 figures, 2 tables, submitted to Ap
Galaxy morphology from z ~ 6 through the lens of JWST
Context: The James Webb Space Telescope's (JWST's) unprecedented combination of sensitivity, spatial resolution, and infrared coverage has enabled a new era of galaxy morphology exploration across most of cosmic history. Aims: We analyze the near-infrared (NIR ~ 0.8 -1 ÎŒm) rest-frame morphologies of galaxies with log Mâ/Mâ > 9 in the redshift range of 0 < z < 6, compare with previous HST-based results and release the first JWST-based morphological catalog of ~20 000 galaxies in the CEERS survey. Methods: We classified the galaxies in our sample into four main broad classes: spheroid, disk+spheroid, disk, and disturbed, based on imaging with four filters: F150W, F200W, F356W, and F444W. We used convolutional neural networks (CNNs) trained on HST/WFC3 labeled images and domain-adapted to JWST/NIRCam. Results: We find that ~90% and ~75% of galaxies at z < 3 have the same early and late and regular and irregular classification, respectively, in JWST and HST imaging when considering similar wavelengths. For small (large) and faint objects, JWST-based classifications tend to systematically present less bulge-dominated systems (peculiar galaxies) than HST-based ones, but the impact on the reported evolution of morphological fractions is less than ~10%. Using JWST-based morphologies at the same rest-frame wavelength ( ~0.8 -1 ÎŒm), we confirm an increase in peculiar galaxies and a decrease in bulge-dominated galaxies with redshift, as reported in previous HST-based works, suggesting that the stellar mass distribution, in addition to light distribution, is more disturbed in the early Universe. However, we find that undisturbed disk-like systems already dominate the high-mass end of the late-type galaxy population (log Mâ/Mâ > 10.5) at z ~ 5, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies ~1 Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at z > 3, with massive quiescent galaxies (log Mâ/Mâ > 10.5) being predominantly bulge-dominated.</p
New insight on the nature of cosmic reionizers from the CEERS survey
The Epoch of Reionization (EoR) began when galaxies grew in abundance and
luminosity, so their escaping Lyman continuum (LyC) radiation started ionizing
the surrounding neutral intergalactic medium (IGM). Despite significant recent
progress, the nature and role of cosmic reionizers are still unclear: in order
to define them, it would be necessary to directly measure their LyC escape
fraction (). However, this is impossible during the EoR due to the
opacity of the IGM. Consequently, many efforts at low and intermediate redshift
have been made to determine measurable indirect indicators in high-redshift
galaxies so that their can be predicted. This work presents the
analysis of the indirect indicators of 62 spectroscopically confirmed
star-forming galaxies at from the Cosmic Evolution Early
Release Science (CEERS) survey, combined with 12 sources with public data from
other JWST-ERS campaigns. From the NIRCam and NIRSpec observations, we measured
their physical and spectroscopic properties. We discovered that on average
star-forming galaxies are compact in the rest-frame UV ( 0.4
kpc), are blue sources (UV- slope -2.17), and have a predicted
of about 0.13.
A comparison of our results to models and predictions as well as an
estimation of the ionizing budget suggests that low-mass galaxies with UV
magnitudes fainter than that we currently do not characterize
with JWST observations probably played a key role in the process of
reionization.Comment: 14 pages, 11 figures, submitted to A&
A Milky Way-like barred spiral galaxy at a redshift of 3
International audienceThe majority of massive disk galaxies in the local Universe show a stellar barred structure in their central regions, including our Milky Way. Bars are supposed to develop in dynamically cold stellar disks at low redshift, as the strong gas turbulence typical of disk galaxies at high redshift suppresses or delays bar formation. Moreover, simulations predict bars to be almost absent beyond in the progenitors of Milky Way-like galaxies. Here we report observations of ceers-2112, a barred spiral galaxy at redshift , which was already mature when the Universe was only 2 Gyr old. The stellar mass () and barred morphology mean that ceers-2112 can be considered a progenitor of the Milky Way, in terms of both structure and mass-assembly history in the first 2 Gyr of the Universe, and was the closest in mass in the first 4 Gyr. We infer that baryons in galaxies could have already dominated over dark matter at , that high-redshift bars could form in approximately 400 Myr and that dynamically cold stellar disks could have been in place by redshift (more than 12 Gyrs ago)
Extremely Red Galaxies at z = 5-9 with MIRI and NIRSpec:Dusty Galaxies or Obscured Active Galactic Nuclei?
We study a new population of extremely red objects (EROs) recently discovered by the James Webb Space Telescope (JWST) based on their NIRCam colors F277W â F444W > 1.5 mag. We find 37 EROs in the Cosmic Evolution Early Release Science Survey (CEERS) field with F444W < 28 mag and photometric redshifts between 5 < z < 7, with median z = 6.9 â 1.6 + 1.0 . Surprisingly, despite their red long-wavelength colors, these EROs have blue short-wavelength colors (F150W â F200W ⌠0 mag) indicative of bimodal spectral energy distributions (SEDs) with a red, steep slope in the rest-frame optical, and a blue, flat slope in the rest-frame UV. Moreover, all these EROs are unresolved, point-like sources in all NIRCam bands. We analyze the SEDs of eight of them with MIRI and NIRSpec observations using stellar population models and active galactic nucleus (AGN) templates. We find that dusty galaxies or obscured AGNs provide similarly good SED fits but different stellar properties: massive and dusty, log M â / M â ⌠10 and A V âł 3 mag, or low mass and obscured, log M â / M â ⌠7.5 and A V ⌠0 mag, hosting an obscured quasi-stellar object (QSO). SED modeling does not favor either scenario, but their unresolved sizes are more suggestive of AGNs. If any EROs are confirmed to have log M â / M â âł 10.5, it would increase the pre-JWST number density at z > 7 by up to a factor âŒ60. Similarly, if they are QSOs with luminosities in the L bol > 1045-46 erg sâ1 range, their number would exceed that of bright blue QSOs by more than three orders of magnitude. Additional photometry at mid-infrared wavelengths will reveal the true nature of the red continuum emission in these EROs and will place this puzzling population in the right context of galaxy evolution.</p
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