ABSTRACT
We present the clump populations detected in 18 lensed galaxies at redshifts 1--8.5 within the lensing cluster field SMACS0723. The recent JWST Early Release Observations of this poorly ...known region of the sky have revealed numerous point-like sources within and surrounding their host galaxies, undetected in the shallower Hubble Space Telescope images. We use JWST multi-and photometry and the lensing model of this galaxy cluster to estimate the intrinsic sizes and magnitudes of the stellar clumps. We derive optical restframe effective radii from <10 to hundreds pc and masses ranging from ∼105 to 109 M ⊙, overlapping with massive star clusters in the local universe. Clump ages range from 1 Myr to 1 Gyr. We compare the crossing time to the age of the clumps and determine that between 45 and 60 per cent of the detected clumps are consistent with being gravitationally bound. On average, the dearth of Gyr old clumps suggests that the dissolution time scales are shorter than 1 Gyr. We see a significant increase in the luminosity (mass) surface density of the clumps with redshift. Clumps in reionization era galaxies have stellar densities higher than star clusters in the local universe. We zoom in into single galaxies at redshift <6 and find for two galaxies, the Sparkler and the Firework, that their star clusters/clumps show distinctive colour distributions and location surrounding their host galaxy that are compatible with being accredited or formed during merger events. The ages of some of the compact clusters are between 1 and 4 Gyr, e.g. globular cluster precursors formed around 9--12 Gyr ago. Our study, conducted on a small sample of galaxies, shows the potential of JWST observations for understanding the conditions under which star clusters form in rapidly evolving galaxies.
Context.
Spectroscopic surveys of massive galaxy clusters reveal the properties of faint background galaxies thanks to the magnification provided by strong gravitational lensing.
Aims.
We present a ...systematic analysis of integral-field-spectroscopy observations of 12 massive clusters, conducted with the Multi Unit Spectroscopic Explorer (MUSE). All data were taken under very good seeing conditions (∼0″.6) in effective exposure times between two and 15 h per pointing, for a total of 125 h. Our observations cover a total solid angle of ∼23 arcmin
2
in the direction of clusters, many of which were previously studied by the MAssive Clusters Survey, Frontier Fields (FFs), Grism Lens-Amplified Survey from Space and Cluster Lensing And Supernova survey with
Hubble
programmes. The achieved emission line detection limit at 5
σ
for a point source varies between (0.77–1.5) × 10
−18
erg s
−1
cm
−2
at 7000 Å.
Methods.
We present our developed strategy to reduce these observational data, detect continuum sources and line emitters in the datacubes, and determine their redshifts. We constructed robust mass models for each cluster to further confirm our redshift measurements using strong-lensing constraints, and identified a total of 312 strongly lensed sources producing 939 multiple images.
Results.
The final redshift catalogues contain more than 3300 robust redshifts, of which 40% are for cluster members and ∼30% are for lensed Lyman-
α
emitters. Fourteen percent of all sources are line emitters that are not seen in the available HST images, even at the depth of the FFs (∼29 AB). We find that the magnification distribution of the lensed sources in the high-magnification regime (
μ
= 2–25) follows the theoretical expectation of
N
(
z
) ∝
μ
−2
. The quality of this dataset, number of lensed sources, and number of strong-lensing constraints enables detailed studies of the physical properties of both the lensing cluster and the background galaxies. The full data products from this work, including the datacubes, catalogues, extracted spectra, ancillary images, and mass models, are made available to the community.
Measurements of stellar properties of galaxies when the universe was less than one billion years old yield some of the only observational constraints on the onset of star formation. We present here ...the inclusion of Spitzer/IRAC imaging in the fitting of the spectral energy distribution of the seven highest-redshift galaxy candidates selected from the Hubble Space Telescope (HST) imaging of the Reionization Lensing Cluster Survey. We find that for six out of eight HST-selected z ∼ 8 sources, the z ∼ 8 solutions are still strongly preferred over z ∼ 1-2 solutions after the inclusion of Spitzer fluxes, and two prefer a z ∼ 7 solution, which we defer to a later analysis. We find a wide range of intrinsic stellar masses (5 × 106-4 × 109 M ), star formation rates (0.2-14 M yr−1), and ages (30-600 Myr) among our sample. Of particular interest is A1763-1434, which shows evidence of an evolved stellar population (∼500 Myr) at z ∼ 8, implying that its first generation of star formation occurred <100 Myr after the Big Bang. SPT0615-JD, a spatially resolved z ∼ 10 candidate, remains at its high redshift, supported by deep Spitzer/IRAC data, and also shows some evidence for an evolved stellar population. Even with the lensed, bright apparent magnitudes of these z 8 candidates (H = 26.1-27.8 AB mag), only the James Webb Space Telescope will be able to exclude the possibility of abnormally strong nebular emission, large dust content, or some combination thereof, and confirm the presence of evolved stellar populations early in the universe.
RELICS: A Strong-lens Model of SMACS J0723.3-7327 Sharon, Keren; Chen, Mandy C.; Mahler, Guillaume ...
The Astrophysical journal. Supplement series,
01/2023, Letnik:
264, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
We present the details of a strong-lens model of SMACS J0723.3-7327, which was made public as part of the data and high-level science products (HLSP) release of the RELICS Hubble Space ...Telescope (HST) treasury program (Reionization Lensing Cluster Survey; GO-14096, PI: Coe). The model products were made available on the Mikulski Archive for Space Telescopes via
10.17909/T9SP45
in 2017. Here, we provide the list of constraints that were used in the HST-based RELICS lens model, as well as other information related to our modeling choices, which were not published with the data and HLSP release. This model was computed with
Lenstool
, used a total of 25 multiple images of eight sources, with no spectroscopic redshifts. The image-plane rms was 0.″58.
Abstract
Star cluster formation in the early universe and its contribution to reionization remains largely unconstrained to date. Here we present JWST/NIRCam imaging of the most highly magnified ...galaxy known at
z
∼ 6, the
Sunrise
arc. We identify six young massive star clusters (YMCs) with measured radii spanning from ∼20 down to ∼1 pc (corrected for lensing magnification), estimated stellar masses of ∼10
6–7
M
⊙
, and ages of 1–30 Myr based on SED fitting to photometry measured in eight filters extending to rest frame 7000 Å. The resulting stellar mass surface densities are higher than 1000
M
⊙
pc
−2
(up to a few 10
5
M
⊙
pc
−2
), and their inferred dynamical ages qualify the majority of these systems as gravitationally bound stellar clusters. The star cluster ages map the progression of star formation along the arc, with two evolved systems (≳10 Myr old) followed by very young clusters. The youngest stellar clusters (<5 Myr) show evidence of prominent H
β
+O
iii
emission based on photometry with equivalent widths larger than >1000 Å rest frame and are hosted in a 200 pc sized star-forming complex. Such a region dominates the ionizing photon production with a high efficiency
log
(
ξ
ion
Hz
erg
−
1
)
∼
25.7
. A significant fraction of the recently formed stellar mass of the galaxy (10%–30%) occurred in these YMCs. We speculate that such sources of ionizing radiation boost the ionizing photon production efficiency, which eventually carves ionized channels that might favor the escape of Lyman continuum radiation. The survival of some of the clusters would make them the progenitors of massive and relatively metal-poor globular clusters in the local universe.
Abstract
Strong gravitational lensing provides unique opportunities to investigate the mass distribution at the cores of galaxy clusters and to study high-redshift galaxies. Using 110 strong-lensing ...models of 74 cluster fields from the Hubble Frontier Fields (HFF), Reionization Lensing Cluster Survey (RELICS), and Sloan Giant Arcs Survey (SGAS), we evaluate the lensing strength of each cluster (area with ∣
μ
∣ ≥ 3 for
z
s
= 9, normalized to a lens redshift of
z
= 0.5). We assess how large-scale mass, projected inner-core mass, and the inner slope of the projected mass-density profile relate to lensing strength. While we do identify a possible trend between lensing strength and large-scale mass (Kendall
τ
= 0.26 and Spearman
r
= 0.36), we find that the inner slope (50 kpc ≤
r
≤ 200 kpc) of the projected mass-density profile has a higher probability of correlation with lensing strength and can set an upper bound on the possible lensing strength of a cluster (Kendall
τ
= 0.53 and Spearman
r
= 0.71). As anticipated, we find that the lensing strength correlates with the effective Einstein area and that a large ( ≳ 30.″0) radial extent of lensing evidence is a strong indicator of a powerful lens. We attribute the spread in the relation to the complexity of individual lensing clusters, which is well captured by the lensing-strength estimator. These results can help us to more efficiently design future observations to use clusters as cosmic telescopes.
Abstract
We report the discovery of four galaxy candidates observed 450–600 Myr after the Big Bang with photometric redshifts between
z
∼ 8.3 and 10.2 measured using James Webb Space Telescope (JWST) ...NIRCam imaging of the galaxy cluster WHL0137−08 observed in eight filters spanning 0.8–5.0
μ
m, plus nine Hubble Space Telescope filters spanning 0.4–1.7
μ
m. One candidate is gravitationally lensed with a magnification of
μ
∼ 8, while the other three are located in a nearby NIRCam module with expected magnifications of
μ
≲ 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range
log
M
⋆
/
M
⊙
= 8.3–8.7. All appear young, with mass-weighted ages <240 Myr, low dust content
A
V
< 0.15 mag, and specific star formation rates sSFR ∼0.25–10 Gyr
−1
for most. One
z
∼ 9 candidate is consistent with an age <5 Myr and an sSFR ∼10 Gyr
−1
, as inferred from a strong F444W excess, implying O
iii
+H
β
rest-frame equivalent width ∼2000 Å, although an older
z
∼ 10 object is also allowed. Another
z
∼ 9 candidate is lensed into an arc 2.″4 long with a magnification of
μ
∼ 8. This arc is the most spatially resolved galaxy at
z
∼ 9 known to date, revealing structures ∼30 pc across. Follow-up spectroscopy of WHL0137−08 with JWST/NIRSpec will be useful to spectroscopically confirm these high-redshift galaxy candidates and to study their physical properties in more detail.
Abstract
We present constraints on the physical properties (including stellar mass, age, and star formation rate) of 207 6 ≲
z
≲ 8 galaxy candidates from the Reionization Lensing Cluster Survey ...(RELICS) and Spitzer-RELICS surveys. We measure photometry using T-PHOT and perform spectral energy distribution fitting using EA
z
Y and BAGPIPES. Of the 207 candidates for which we could successfully measure (or place limits on) Spitzer fluxes, 23 were demoted to likely
z
< 4. Among the high-
z
candidates, we find intrinsic stellar masses between 1 × 10
6
M
⊙
and 4 × 10
9
M
⊙
, and rest-frame UV absolute magnitudes between −22.6 and −14.5 mag. While our sample is mostly comprised of
L
m
UV
/
L
m
UV
*
<
1
galaxies, it extends to
L
m
UV
/
L
m
UV
*
∼
2
. Our sample spans ∼4 orders of magnitude in stellar mass and star formation rates, and exhibits ages that range from maximally young to maximally old. We highlight 11
z
≥ 6.5 galaxies with detections in Spitzer/IRAC imaging, several of which show evidence for some combination of evolved stellar populations, large contributions of nebular emission lines, and/or dust. Among these is PLCKG287+32-2013, one of the brightest
z
∼ 7 candidates known (AB mag 24.9 at 1.6
μ
m) with a Spitzer 3.6
μ
m flux excess suggesting strong O
iii
+ H-
β
emission (∼1000 Å rest-frame equivalent width). We discuss the possible uses and limits of our sample and present a public catalog of Hubble + Spitzer photometry along with physical property estimates for all objects in the sample. Because of their apparent brightnesses, high redshifts, and variety of stellar populations, these objects are excellent targets for follow-up with the James Webb Space Telescope.
Abstract
Exploiting the fundamentally achromatic nature of gravitational lensing, we present a lens model for the massive galaxy cluster SMACS J0723.3−7323 (SMACS J0723;
z
= 0.388) that significantly ...improves upon earlier work. Building on strong-lensing constraints identified in prior Hubble Space Telescope (HST) observations, the mass model utilizes 21 multiple-image systems, 17 of which were newly discovered in Early Release Observation data from the JWST. The resulting lens model maps the cluster mass distribution to an rms spatial precision of 0.″32, and is publicly available. Consistent with previous analyses, our study shows SMACS J0723.3 to be well described by a single large-scale component centered on the location of the brightest cluster galaxy. However, satisfying all lensing constraints provided by the JWST data, the model points to the need for the inclusion of an additional, diffuse component west of the cluster. A comparison of the galaxy, mass, and gas distributions in the core of SMACS J0723 based on HST, JWST, and Chandra data reveals a concentrated regular elliptical profile along with tell-tale signs of a recent merger, possibly proceeding almost along our line of sight. The exquisite sensitivity of JWST’s NIRCam reveals in spectacular fashion both the extended intracluster light distribution and numerous star-forming clumps in magnified background galaxies. The high-precision lens model derived here for SMACS J0723 demonstrates the unprecedented power of combining HST and JWST data for studies of structure formation and evolution in the distant universe.
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