4 research outputs found
Early results from GLASS-JWST. XX: Unveiling a population of "red-excess'' galaxies in Abell2744 and in the coeval field
We combine JWST/NIRCam imaging and MUSE data to characterize the properties
of galaxies in different environmental conditions in the cluster Abell2744
() and in its immediate surroundings. We investigate how galaxy
colors, morphology and star forming fractions depend on wavelength and on
different parameterizations of environment. Our most striking result is the
discovery of a ``red-excess'' population in F200WF444W colors both in the
cluster regions and the field. These galaxies have normal F115WF150W colors,
but are up to 0.8 mag redder than red sequence galaxies in F200WF444W. They
also have rather blue rest frame BV colors. {Galaxies in the field and at
the cluster virial radius are overall characterized by redder colors, but
galaxies with the largest color deviations are found in the field and in the
cluster core. Several results} suggest that mechanisms taking place in these
regions might be more effective in producing these colors. Looking at their
morphology, many cluster galaxies show signatures consistent with ram pressure
stripping, while field galaxies have features resembling interactions and
mergers. Our hypothesis is that these galaxies are characterized by dust
enshrouded star formation: a JWST/NIRSpec spectrum for one of the galaxies is
dominated by a strong PAH at 3.3, suggestive of dust obscured star
formation. Larger spectroscopic samples are needed to understand if the color
excess is due exclusively to dust-obscured star formation, and the role of
environment in triggering it.Comment: ApJL in pres
A shot in the Dark (Ages): a faint galaxy at confirmed with JWST
The appearance of galaxies over the first billion years after the Big Bang is
believed to be responsible for the last dramatic change in the state of the
Universe. Ultraviolet photons from galaxies within this time period - the Epoch
of Reionization - ionized intergalactic Hydrogen, rendering the Universe
transparent to UV radiation and ending the so-called cosmic Dark Ages, sometime
after redshift . The majority of ionizing photons in the first few
hundred Myrs of cosmic history are thought to derive from galaxies
significantly fainter than the characteristic luminosity . These faint
galaxies are thought to be surrounded by sufficient neutral gas to prevent the
escape of the Lyman- photons that would allow confirmation with current
observatories. Here we demonstrate the power of the recently commissioned James
Webb Space Telescope to transform our understanding of the sources of
reionization, by reporting the first spectroscopic confirmation of a very low
luminosity () galaxy at , observed 480 Myr after the
Big Bang, via the detection of the Lyman-break and redward continuum with the
NIRSpec and NIRCam instruments. The galaxy JD1 is gravitationally magnified by
a factor of by the foreground cluster A2744. The power of JWST and
lensing allows us to peer deeper than ever before into the cosmic Dark Ages,
revealing the compact (150 pc) and complex morphology and physical
properties of an ultrafaint galaxy ().Comment: Submitted to Nature. 34 pages, 4 main figures, 1 supplementary
figure, 2 supplementary tables. Comments are welcom
JADES Initial Data Release for the Hubble Ultra Deep Field: Revealing the Faint Infrared Sky with Deep JWST NIRCam Imaging
JWST has revolutionized the field of extragalactic astronomy with its
sensitive and high-resolution infrared view of the distant universe. Adding to
the new legacy of JWST observations, we present the first NIRCam imaging data
release from the JWST Advanced Deep Extragalactic Survey (JADES) providing 9
filters of infrared imaging of 25 arcmin covering the Hubble Ultra
Deep Field and portions of Great Observatories Origins Deep Survey (GOODS)
South. Utilizing 87 on-sky dual-filter hours of exposure time, these images
reveal the deepest ever near-infrared view of this iconic field. We supply
carefully constructed 9-band mosaics of the JADES bands, as well as matching
reductions of 5 additional bands from the JWST Extragalactic Medium-band Survey
(JEMS). Combining with existing HST imaging, we provide 23-band space-based
photometric catalogs and photometric redshifts for sources. To
promote broad engagement with the JADES survey, we have created an interactive
{\tt FitsMap} website to provide an interface for professional researchers and
the public to experience these JWST datasets. Combined with the first JADES
NIRSpec data release, these public JADES imaging and spectroscopic datasets
provide a new foundation for discoveries of the infrared universe by the
worldwide scientific community.Comment: Several figures were modified to use better line styles. A brief
comparison to IRAC Channel 1 photometry was added along with a few other
clarifications. Paper has been accepted for publication in ApJ
Early Results from GLASS-JWST. XXII. Rest-frame UV–Optical Spectral Properties of Lyα Emitting Galaxies at 3 < z < 6
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 ), 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 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