980 research outputs found
Stellar Properties of z ~ 8 Galaxies in the Reionization Lensing Cluster Survey
Measurements of stellar properties of galaxies when the universe was less
than one billion years old yield some of the only observational constraints of
the onset of star formation. We present here the inclusion of
\textit{Spitzer}/IRAC imaging in the spectral energy distribution fitting of
the seven highest-redshift galaxy candidates selected from the \emph{Hubble
Space Telescope} imaging of the Reionization Lensing Cluster Survey (RELICS).
We find that for 6/8 \textit{HST}-selected sources, the
solutions are still strongly preferred over 1-2 solutions after the
inclusion of \textit{Spitzer} fluxes, and two prefer a solution,
which we defer to a later analysis. We find a wide range of intrinsic stellar
masses ( -- ), star formation
rates (0.2-14 ), and ages (30-600 Myr) among our sample.
Of particular interest is Abell1763-1434, which shows evidence of an evolved
stellar population at , implying its first generation of star formation
occurred just Myr after the Big Bang. SPT0615-JD, a spatially resolved
candidate, remains at its high redshift, supported by deep
\textit{Spitzer}/IRAC data, and also shows some evidence for an evolved stellar
population. Even with the lensed, bright apparent magnitudes of these candidates (H = 26.1-27.8 AB mag), only the \textit{James Webb Space
Telescope} will be able further confirm the presence of evolved stellar
populations early in the universe.Comment: 8 pages, 3 figures, 2 table
The archival discovery of a strong Lyman- and [CII] emitter at z = 7.677
We report the archival discovery of Lyman- emission from the bright
ultraviolet galaxy Y002 at , spectroscopically confirmed by its
ionized carbon [CII] 158m emission line. The Ly line is spatially
associated with the rest-frame UV stellar emission (~-22, 2x
brighter than ) and it appears offset from the peak of the
extended [CII] emission at the current ~1" spatial resolution. We derive an
estimate of the unobscured SFR(UV)= yr and set an
upper limit of SFR(IR) yr from the far-infrared wavelength
range, which globally place Y002 on the SFR(UV+IR)-L([CII]) correlation
observed at lower redshifts. In terms of velocity, the peak of the Ly
emission is redshifted by (Ly)~500 km s from the
systemic redshift set by [CII] and a high-velocity tail extends to up to ~1000
km s. The velocity offset is up to ~3.5x higher than the average
estimate for similarly UV-bright emitters at z~6-7, which might suggest that we
are witnessing the merging of two clumps. A combination of strong outflows and
the possible presence of an extended ionized bubble surrounding Y002 would
likely facilitate the escape of copious Ly light, as indicated by the
large equivalent width EW(Ly)= \r{A}. Assuming that [CII]
traces the neutral hydrogen, we estimate a HI gas fraction of for Y002 as a system and speculate that patches of high
HI column densities could contribute to explain the observed spatial offsets
between Ly and [CII] emitting regions. The low dust content, implied by
the non-detection of the far-infrared continuum emission at rest-frame ~160
m, would be sufficient to absorb any potential Ly photons produced
within the [CII] clump as a result of large HI column densities.Comment: 10 pages, 4 figures. Accepted for publication in The Astrophysical
Journal Letter
CANUCS: An Updated Mass and Magnification Model of Abell 370 with JWST
We report an updated mass and magnification model of galaxy cluster Abell 370
using new NIRCam and NIRISS data from the CAnadian NIRISS Unbiased Cluster
Survey (CANUCS). Using Lenstool and a combination of archival HST and MUSE data
with new JWST data as constraints, we derive an improved gravitational lensing
model and extract magnifications of background galaxies with uncertainties.
Using our best fit model, we perform a search for new multiply imaged systems
via predicted positions. We report no new multiply imaged systems with
identifiable redshifts, likely due to already very deep HST and Spitzer data,
but confirm a multiply imaged system by measuring its redshift with
NIRISS and NIRSpec spectra. We find that the overall shape of the critical
curve for a source at is similar to previous models of Abell 370,
with small changes. We investigate the galaxy with two images
observable with an apparent magnitude in the F125W band of and
. After correcting for the magnifications of the images,
7.2 and 8.7, we use SED fitting to find an
intrinsic stellar mass of log( = 7.35,
intrinsic SFR of 3.5 M/yr, and of
-21.3, which is close to the knee of the luminosity function at
that redshift. Our model, and corresponding magnification, shear, and
convergence maps are available on request and will be made publicly available
on MAST in a CANUCS data release (DOI: 10.17909/ph4n-6n76).Comment: 15 page
A First Look at Spatially Resolved Balmer Decrements at from JWST NIRISS Slitless Spectroscopy
We present the first results on the spatial distribution of dust attenuation
at traced by the Balmer Decrement, H/H, in
emission-line galaxies using deep JWST NIRISS slitless spectroscopy from the
CAnadian NIRISS Unbiased Cluster Survey (CANUCS). H and H
emission line maps of emission-line galaxies are extracted and stacked in bins
of stellar mass for two grism redshift bins, and
. Surface brightness profiles for the Balmer Decrement are
measured and radial profiles of the dust attenuation towards H,
, are derived. In both redshift bins, the integrated
Balmer Decrement increases with stellar mass. Lower mass
(Log(/M)) galaxies have centrally
concentrated, negative dust attenuation profiles whereas higher mass galaxies
(Log(/M)) have flat dust attenuation
profiles. The total dust obscuration is mild, with on average and
mag in the low and high redshift bins respectively. We model the
typical light profiles of star-forming galaxies at these redshifts and stellar
masses with GALFIT and apply both uniform and radially varying dust attenuation
corrections based on our integrated Balmer Decrements and radial dust
attenuation profiles. If these galaxies were observed with typical JWST NIRSpec
slit spectroscopy ( shutters), on average,
H star formation rates (SFRs) measured after slit-loss corrections
assuming uniform dust attenuation will overestimate the total SFR by and at and
respectively.Comment: 7 pages, 5 figures, submitted to ApJ
RELICS: High-Resolution Constraints on the Inner Mass Distribution of the z=0.83 Merging Cluster RXJ0152.7-1357 from strong lensing
Strong gravitational lensing (SL) is a powerful means to map the distribution
of dark matter. In this work, we perform a SL analysis of the prominent X-ray
cluster RXJ0152.7-1357 (z=0.83, also known as CL 0152.7-1357) in \textit{Hubble
Space Telescope} images, taken in the framework of the Reionization Lensing
Cluster Survey (RELICS). On top of a previously known galaxy multiply
imaged by RXJ0152.7-1357, for which we identify an additional multiple image,
guided by a light-traces-mass approach we identify seven new sets of multiply
imaged background sources lensed by this cluster, spanning the redshift range
[1.79-3.93]. A total of 25 multiple images are seen over a small area of ~0.4
, allowing us to put relatively high-resolution constraints on the
inner matter distribution. Although modestly massive, the high degree of
substructure together with its very elongated shape make RXJ0152.7-1357 a very
efficient lens for its size. This cluster also comprises the third-largest
sample of z~6-7 candidates in the RELICS survey. Finally, we present a
comparison of our resulting mass distribution and magnification estimates with
those from a Lenstool model. These models are made publicly available through
the MAST archive.Comment: 15 Pages, 7 Figures, 4 Tables Accepted for publication in Ap
Bursty star formation and galaxy-galaxy interactions in low-mass galaxies 1 Gyr after the Big Bang
We use CANUCS JWST/NIRCam imaging of galaxies behind the
gravitationally-lensing cluster MACS J0417.5-1154 to investigate star formation
burstiness in low-mass () galaxies at .
Our sample of 123 galaxies is selected using the Lyman break selection and
photometric emission-line excess methods. Sixty per cent of the 123 galaxies in
this sample have H-to-UV flux ratios that deviate significantly from
the range of values consistent with smooth and steady star
formation histories. This large fraction indicates that the majority of
low-mass galaxies is experiencing bursty star formation histories at high
redshift. We also searched for interacting galaxies in our sample and found
that they are remarkably common ( per cent of the sample). Compared to
non-interacting galaxies, interacting galaxies are more likely to have very low
H-to-UV ratios, suggesting that galaxy-galaxy interactions enhance star
formation burstiness and enable faster quenching (with timescales of
Myr) that follows the rapid rise of star formation activity.
Given the high frequency of galaxy-galaxy interactions and the rapid SFR
fluctuations they appear to cause, we conclude that galaxy-galaxy interactions
could be a leading cause of bursty star formation in low-mass, high-
galaxies. They could thus play a significant role in the evolution of the
galaxy population at early cosmological times.Comment: 20 pages, 15 figures, and 1 table. Accepted for publication in MNRA
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