120 research outputs found
Redshifting galaxies from DESI to JWST CEERS: Correction of biases and uncertainties in quantifying morphology
Observations of high-redshift galaxies with unprecedented detail have now
been rendered possible with JWST. However, accurately quantifying their
morphology remains uncertain due to potential biases and uncertainties. To
address this issue, we used a sample of 1816 nearby DESI galaxies, with a mass
range of , to compute artificial images of galaxies
of the same mass located at and observed at rest-frame
optical wavelength in CEERS. We analyzed the effects of cosmological redshift
on the measurements of Petrosian radius (), half-light radius (),
asymmetry (), concentration (), axis ratio (), and S\'ersic index
(). Our results show that and , calculated using
non-parametric methods, are slightly overestimated due to PSF smoothing, while
, , and obtained through model fitting does not exhibit
significant biases. We improve the computation of by incorporating a more
accurate noise effect removal procedure. Due to PSF asymmetry, there is a minor
overestimation of for intrinsically symmetric galaxies. However, for
intrinsically asymmetric galaxies, PSF smoothing dominates and results in an
underestimation of , an effect that becomes more significant with higher
intrinsic or at lower resolutions. Moreover, PSF smoothing also leads to an
underestimation of , which is notably more pronounced in galaxies with
higher intrinsic or at lower resolutions. We developed functions based on
resolution level, defined as FWHM, for correcting these biases and the
associated statistical uncertainties. Applying these corrections, we measured
the bias-corrected morphology for the simulated CEERS images and we find that
the derived quantities are in good agreement with their intrinsic values --
except for , which is robust only for angularly large galaxies where
.Comment: 21 pages, 17 figures; A&A in pres
Luminous Lyman-alpha Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 <= z <= 6.6
We study six luminous Lyman-alpha emitters (LAEs) with very blue rest-frame
UV continua at . These LAEs have previous HST and Spitzer
IRAC observations. Combining our newly acquired HST images, we find that their
UV-continuum slopes are in a range of . Unlike
previous, tentative detections of in photometrically
selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and
luminous ( mag). We model their broadband spectral energy
distributions (SEDs), and find that two galaxies can be
well fitted with young and dust-free stellar populations. However, it becomes
increasingly difficult to fit bluer galaxies. We explore further
interpretations by including non-zero LyC escape fraction , very
low metallicities, and/or AGN contributions. Assuming ,
we achieve the bluest slopes when nebular emission is
considered. This can nearly explain the SEDs of two galaxies with
and --2.9 (). Larger
values and very low metallicities are not favored by the strong nebular line
emission (evidenced by the IRAC flux) or the observed (IRAC 1 - IRAC 2) color.
Finally, we find that the galaxy can potentially be well
explained by the combination of a very young population with a high () and an old, dusty population. We are not able to produce two
galaxies. Future deep spectroscopic observations are
needed to fully understand these galaxies.Comment: Published in ApJ on 2020 Feb 1; Authors' version (9 pages); See
published version at
https://iopscience.iop.org/article/10.3847/1538-4357/ab64e
The Mass-Metallicity Relation of Dwarf Galaxies at the Cosmic Noon in the JWST Era
We present the mass-metallicity relation (MZR) at in the stellar mass
range of using 55 dwarf galaxies in
the Abell 2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf galaxies
are identified and confirmed by deep JWST/NIRISS imaging and slitless grism
spectroscopic observations. Taking advantage of the gravitational lensing
effect, we extend the previous MZR relation at to a much lower mass
regime by more than 2.5 orders of magnitude compared with previous studies. We
find that the MZR has a shallower slope at the low-mass end
() compared to that at the high-mass end
(), with a slope turnover point at around the stellar
mass of . This implies that dominating feedback processes in
dwarf galaxies may be different from that in galaxies with higher mass. From
to , the metallicity of the dwarf galaxies is enhanced by
dex for a given stellar mass, consistent with the mild evolution
found in galaxies with higher mass. Further, we confirm the existence of a 3D
relation between the gas-phase metallicity, stellar mass, and star formation
rate, i.e., fundamental metallicity relation (FMR), in dwarf galaxies at
. Our derived FMR, which has no significant redshift evolution, can be
used as a benchmark to understand the origin of the anti-correlation between
SFR and metallicity of dwarf galaxies in the high-redshift Universe.Comment: 16 pages, 4 figures, 1 table, submitted to AAS Journal; welcome
comment
JWST and ALMA imaging of dust-obscured, massive substructures in a typical star-forming disk galaxy
We present an identification of dust-attenuated star-forming galactic-disk
substructures in a typical star-forming galaxy (SFG), UDF2, at . To
date, substructures containing significant buildup of stellar mass and actively
forming stars have yet to be found in typical (i.e., main-sequence) SFGs at . This is due to the strong dust attenuation common in massive galaxies at
the epoch and the scarcity of high-resolution, high-sensitivity
extinction-independent imaging. To search for disk substructures, we subtracted
the central stellar-mass disk from the JWST/NIRCam rest-frame 1.2 m image
( resolution) and subtracted, in the visibility plane, the central
starburst disk from ALMA rest-frame 240 m observations (
resolution). The residual images revealed substructures at rest-frame 1.2
m co-located with those found at rest-frame 240 m, kpc
away from the galactic center. The largest substructure contains % of
the total stellar mass and % of the total SFR of the galaxy. While
UDF2 exhibits a kinematically-ordered velocity field of molecular gas
consistent with a secularly evolving disk, more sensitive observations are
required to characterize the nature and the origin of this substructure (spiral
arms, minor merger, or other types of disk instabilities). UDF2 resides in an
overdense region ( massive galaxies within 70 kpc projected
distance at ) and the substructures may be associated with
interaction-induced instabilities. Importantly, a statistical sample of such
substructures identified with JWST and ALMA could play a key role in bridging
the gap between the bulge-forming starburst and the rest of the galaxy.Comment: 7 pages, 5 figures; ApJL, accepte
ALMA Lensing Cluster Survey: Properties of Millimeter Galaxies Hosting X-ray Detected Active Galactic Nuclei
We report the multi-wavelength 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 over 33 clusters with a 1.2 mm
flux-density limit of 60 (). Utilizing the
archival data of Chandra, we identify three AGNs at 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 (), while the other shows signs of moderate absorption (). We also perform spectral energy
distribution (SED) modelling 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 ) and
star-formation rates (). This
demonstrates that a wide-area survey with ALMA and Chandra can selectively
detect intense growth of both galaxies and supermassive black holes (SMBHs) in
the high-redshift universe.Comment: 14 pages, 3 figures, 2 table
ALMA Lensing Cluster Survey: Full Spectral Energy Distribution Analysis of z ∼ 0.5–6 Lensed Galaxies Detected with millimeter Observations
Sub/millimeter galaxies are a key population for the study of galaxy evolution because the majority of star formation at high redshifts occurred in galaxies deeply embedded in dust. To search for this population, we have performed an extensive survey with Atacama Large Millimeter/submillimeter Array (ALMA), called the ALMA Lensing Cluster Survey (ALCS). This survey covers 133 arcmin2 area and securely detects 180 sources at z ∼ 0.5–6 with a flux limit of ∼0.2 mJy at 1.2 mm. Here, we report the results of multiwavelength spectral energy distribution analysis of the whole ALCS sample, utilizing the observed-frame UV to millimeter photometry. We find that the majority of the ALCS sources lie on the star-forming main sequence, with a smaller fraction showing intense starburst activities. The ALCS sample contains high infrared-excess sources ( IRX=log(Ldust/LUV)>1 ), including two extremely dust-obscured galaxies (IRX > 5). We also confirm that the ALCS sample probes a broader range in lower dust mass than conventional submillimeter galaxy samples in the same redshift range. We identify six heavily obscured active galactic nucleus (AGN) candidates that are not detected in the archival Chandra data in addition to the three X-ray AGNs reported by Uematsu et al. (2023). The inferred AGN luminosity density shows a possible excess at z = 2–3 compared with that determined from X-ray surveys below 10 keV
Metal-Enriched Neutral Gas Reservoir around a Strongly-lensed, Low-mass Galaxy at Identified by JWST/NIRISS and VLT/MUSE
Direct observations of low-mass, low-metallicity galaxies at
provide an indispensable opportunity for detailed inspection of the ionization
radiation, gas flow, and metal enrichment in sources similar to those that
reionized the Universe. Combining the James Webb Space Telescope (JWST),
VLT/MUSE, and ALMA, we present detailed observations of a strongly lensed,
low-mass ( ) galaxy at (also see
Vanzella et al. 2022). We identify strong narrow nebular emission, including
CIV , HeII , OIII]
, [NeIII] , [OII] , and
Balmer series of Hydrogen from this galaxy, indicating a metal-poor HII region
() powered by massive stars. Further, we detect a
metal-enriched damped Ly system (DLA) associated with the galaxy with
the HI column density of cm. The
metallicity of the associated DLA may reach the super solar metallicity
(). Moreover, thanks to JWST and gravitational lensing, we
present the resolved UV slope () map at the spatial resolution of
pc at , with steep UV slopes reaching
around three star-forming clumps. Combining with low-redshift analogs, our
observations suggest that low-mass, low-metallicity galaxies, which dominate
reionization, could be surrounded by a high covering fraction of the
metal-enriched, neutral-gaseous clouds. This implies that the metal enrichment
of low-mass galaxies is highly efficient, and further support that in low-mass
galaxies, only a small fraction of ionizing radiation can escape through the
interstellar or circumgalactic channels with low column-density neutral gas.Comment: 4 pages, 1 table; submitted to the ApJL; welcome comment
JADES: Using NIRCam Photometry to Investigate the Dependence of Stellar Mass Inferences on the IMF in the Early Universe
The detection of numerous and relatively bright galaxies at redshifts z > 9
has prompted new investigations into the star-forming properties of
high-redshift galaxies. Using local forms of the initial mass function (IMF) to
estimate stellar masses of these galaxies from their light output leads to
galaxy masses that are at the limit allowed for the state of the LambdaCDM
Universe at their redshift. We explore how varying the IMF assumed in studies
of galaxies in the early universe changes the inferred values for the stellar
masses of these galaxies. We infer galaxy properties with the SED fitting code
Prospector using varying IMF parameterizations for a sample of 102 galaxies
from the JWST Advanced Deep Extragalactic Survey (JADES) spectroscopically
confirmed to be at z > 6.7, with additional photometry from the JWST
Extragalactic Medium Band Survey (JEMS) for twenty-one galaxies. We demonstrate
that models with stellar masses reduced by a factor of three or more do not
affect the modeled spectral energy distribution (SED).Comment: The Significance statement is required for PNAS submissio
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