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.
Massive foreground galaxy clusters magnify and distort the light of objects behind them, permitting a view into both the extremely distant and intrinsically faint galaxy populations. We present here ...the candidate high-redshift galaxies from the Reionization Lensing Cluster Survey (RELICS), a Hubble and Spitzer Space Telescope survey of 41 massive galaxy clusters spanning an area of 200 arcmin2. These clusters were selected to be excellent lenses, and we find similar high-redshift sample sizes and magnitude distributions as the Cluster Lensing And Supernova survey with Hubble (CLASH). We discover 257, 57, and eight candidate galaxies at z ∼ 6, 7, and 8 respectively, (322 in total). The observed (lensed) magnitudes of the z ∼ 6 candidates are as bright as AB mag ∼23, making them among the brightest known at these redshifts, comparable with discoveries from much wider, blank-field surveys. RELICS demonstrates the efficiency of using strong gravitational lenses to produce high-redshift samples in the epoch of reionization. These brightly observed galaxies are excellent targets for follow-up study with current and future observatories, including the James Webb Space Telescope.
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.
Strong gravitational lensing by galaxy clusters magnifies background galaxies, enhancing our ability to discover statistically significant samples of galaxies at , in order to constrain the ...high-redshift galaxy luminosity functions. Here, we present the first five lens models out of the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury Program, based on new HST WFC3/IR and ACS imaging of the clusters RXC J0142.9+4438, Abell 2537, Abell 2163, RXC J2211.7-0349, and ACT-CLJ0102-49151. The derived lensing magnification is essential for estimating the intrinsic properties of high-redshift galaxy candidates, and properly accounting for the survey volume. We report on new spectroscopic redshifts of multiply imaged lensed galaxies behind these clusters, which are used as constraints, and detail our strategy to reduce systematic uncertainties due to lack of spectroscopic information. In addition, we quantify the uncertainty on the lensing magnification due to statistical and systematic errors related to the lens modeling process, and find that in all but one cluster, the magnification is constrained to better than 20% in at least 80% of the field of view, including statistical and systematic uncertainties. The five clusters presented in this paper span the range of masses and redshifts of the clusters in the RELICS program. We find that they exhibit similar strong lensing efficiencies to the clusters targeted by the Hubble Frontier Fields within the WFC3/IR field of view. Outputs of the lens models are made available to the community through the Mikulski Archive for Space Telescopes.
We present a lens model for the cluster SPT-CLJ0615−5746, which is the highest-redshift (z = 0.972) system in the Reionization of Lensing Clusters Survey, making it the highest-redshift cluster for ...which a full, strong lens model is published. We identify three systems of multiply imaged lensed galaxies, two of which we spectroscopically confirm at z = 1.358 and z = 4.013, which we use as constraints for the model. We find a foreground structure at z ∼ 0.4, which we include as a second cluster-sized halo in one of our models; however, two different statistical tests find the best-fit model consists of one cluster-sized halo combined with three individually optimized galaxy-sized halos, as well as contributions from the cluster galaxies themselves. We find the total projected mass density within r = 26 7 (the region where the strong lensing constraints exist) to be M☉. If we extrapolate out to r500, our projected mass density is consistent with the mass inferred from weak lensing and from the Sunyaev-Zel'dovich effect (M ∼ 1015 M☉). This cluster is lensing a previously reported z ∼ 10 galaxy, which, if spectroscopically confirmed, will be the highest-redshift strongly lensed galaxy known.
Extensive surveys with the Hubble Space Telescope over the past decade, targeting some of the most massive clusters in the sky, have uncovered dozens of galaxy cluster strong lenses. The massive ...cluster strong-lens scale is typically θE ∼ 10″ to ∼30″-35″, with only a handful of clusters known with Einstein radii θE ∼ 40″ or above (for zsource = 2, nominally). Here we report another very large cluster lens, RXC J0032.1+1808 (z = 0.3956), the second-richest cluster in the redMapper cluster catalog and the 85th most massive cluster in the Planck Sunyaev-Zel'dovich catalog. With our light-traces-mass and fully parametric approaches, we construct strong-lensing models based on 18 multiple images of five background galaxies newly identified in the Hubble data, mainly from the Reionization Lensing Cluster Survey (RELICS), in addition to a known sextuply imaged system in this cluster. Furthermore, we compare these models to Lenstool and GLAFIC models that were produced independently as part of the RELICS program. All models reveal a large effective Einstein radius of θE 40″ (zsource = 2), owing to the obvious concentration of substructures near the cluster center. Although RXC J0032.1+1808 has a very large critical area and high lensing strength, only three magnified high-redshift candidates are found within the field targeted by RELICS. Nevertheless, we expect many more high-redshift candidates will be seen in wider and deeper observations with Hubble or the James Webb Space Telescope. Finally, the comparison between several algorithms demonstrates that the total error budget is largely dominated by systematic uncertainties.
ABSTRACT We present results from recent Suzaku and Chandra X-ray and Multiple Mirrior Telescope optical observations of the strongly merging "double cluster" A1750 out to its virial radius, both ...along and perpendicular to a putative large-scale structure filament. Some previous studies of individual clusters have found evidence for ICM entropy profiles that flatten at large cluster radii, as compared with the self-similar prediction based on purely gravitational models of hierarchical cluster formation, and gas fractions that rise above the mean cosmic value. Weakening accretion shocks and the presence of unresolved cool gas clumps, both of which are expected to correlate with large-scale structure filaments, have been invoked to explain these results. In the outskirts of A1750, we find entropy profiles that are consistent with self-similar expectations, and gas fractions that are consistent with the mean cosmic value, both along and perpendicular to the putative large-scale filament. Thus, we find no evidence for gas clumping in the outskirts of A1750, in either direction. This may indicate that gas clumping is less common in lower temperature (kT 4 keV), less massive systems, consistent with some (but not all) previous studies of low-mass clusters and groups. Cluster mass may, therefore, play a more important role in gas clumping than dynamical state. Finally, we find evidence for diffuse, cool (<1 keV) gas at large cluster radii (R200) along the filament, which is consistent with the expected properties of the denser, hotter phase of the warm-hot intergalactic medium.
We stack the rest-frame ultraviolet spectra of N = 14 highly magnified gravitationally lensed galaxies at redshifts . The resulting new composite spans , with a peak signal-to-noise ratio (S/N) of ...103 per spectral resolution element (∼100 km s−1). It is the highest S/N, highest spectral resolution composite spectrum of z ∼ 2-3 galaxies yet published. The composite reveals numerous weak nebular emission lines and stellar photospheric absorption lines that can serve as new physical diagnostics, particularly at high redshift with the James Webb Space Telescope (JWST). We report equivalent widths to aid in proposing for and interpreting JWST spectra. We examine the velocity profiles of strong absorption features in the composite, and in a matched composite of COS/HST galaxy spectra. We find remarkable similarity in the velocity profiles at and , suggesting that similar physical processes control the outflows across cosmic time. While the maximum outflow velocity depends strongly on ionization potential, the absorption-weighted mean velocity does not. As such, the bulk of the high-ionization absorption traces the low-ionization gas, with an additional blueshifted absorption tail extending to at least −2000 km s−1. We interpret this tail as arising from the stellar wind and photospheres of massive stars. Starburst99 models are able to replicate this high-velocity absorption tail. However, these theoretical models poorly reproduce several of the photospheric absorption features, indicating that improvements are needed to match observational constraints on the massive stellar content of star-forming galaxies at . We publicly release our composite spectra.
We introduce Project MegaSaura: the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MegaSaura comprises medium-resolution, rest-frame ultraviolet spectroscopy of N = 15 ...bright gravitationally lensed galaxies at redshifts of 1.68 < z < 3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range 3200 < λo < 8280 ; the average spectral resolving power is R = 3300. The median spectrum has a signal-to-noise ratio (S/N) = 21 per resolution element at 5000 . As such, the MegaSaura spectra have superior S/N and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum. We provide the MegaSaura spectra to the astronomical community through a data release.
Abstract
We present strong gravitational lensing models for 37 galaxy clusters from the Sloan Digital Sky Survey Giant Arcs Survey. We combine data from multi-band
Hubble Space Telescope
Wide Field ...Camera 3 (WFC3) imaging, with ground-based imaging and spectroscopy from
Magellan
, Gemini, Apache Point Observatory, and the Multiple Mirror Telescope, in order to detect and spectroscopically confirm new multiply imaged lensed background sources behind the clusters. We report spectroscopic or photometric redshifts of sources in these fields, including cluster galaxies and background sources. Based on all available lensing evidence, we construct and present strong-lensing mass models for these galaxy clusters. The clusters span a redshift range of 0.176 <
z
< 0.66 with a median redshift of
z
= 0.45, and sample a wide range of dynamical masses, 1.5 <
M
200
< 35 × 10
14
, as estimated from their velocity dispersions. As these clusters were selected as lenses primarily owing to a fortuitous alignment with background galaxies that results in giant arcs, they exhibit a wide range in Einstein radii, 1.″3 <
θ
E
< 23.″1 for a source at
z
= 2, with a median
θ
E
= 10.″8. The reduced
HST
images and lens model outputs are made available to the scientific community as high-level data products with this publication.
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