Large surveys of galaxy clusters with the Hubble and Spitzer Space Telescopes, including CLASH and the Frontier Fields, have demonstrated the power of strong gravitational lensing to efficiently ...deliver large samples of high-redshift galaxies. We extend this strategy through a wider, shallower survey named RELICS, the Reionization Lensing Cluster Survey. This survey, described here, was designed primarily to deliver the best and brightest high-redshift candidates from the first billion years after the Big Bang. RELICS observed 41 massive galaxy clusters with Hubble and Spitzer at 0.4-1.7um and 3.0-5.0um, respectively. We selected 21 clusters based on Planck PSZ2 mass estimates and the other 20 based on observed or inferred lensing strength. Our 188-orbit Hubble Treasury Program obtained the first high-resolution near-infrared images of these clusters to efficiently search for lensed high-redshift galaxies. We observed 46 WFC3/IR pointings (~200 arcmin^2) with two orbits divided among four filters (F105W, F125W, F140W, and F160W) and ACS imaging as needed to achieve single-orbit depth in each of three filters (F435W, F606W, and F814W). As previously reported by Salmon et al., we discovered 322 z ~ 6 - 10 candidates, including the brightest known at z ~ 6, and the most distant spatially-resolved lensed arc known at z ~ 10. Spitzer IRAC imaging (945 hours awarded, plus 100 archival) has crucially enabled us to distinguish z ~ 10 candidates from z ~ 2 interlopers. For each cluster, two HST observing epochs were staggered by about a month, enabling us to discover 11 supernovae, including 3 lensed supernovae, which we followed up with 20 orbits from our program. We delivered reduced HST images and catalogs of all clusters to the public via MAST and reduced Spitzer images via IRSA. We have also begun delivering lens models of all clusters, to be completed before the JWST GO call for proposals.
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 \(z=3.93\) 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 \(arcmin^2\), 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.
The most distant galaxies known are at z~10-11, observed 400-500 Myr after
the Big Bang. The few z~10-11 candidates discovered to date have been
exceptionally small- barely resolved, if at all, by ...the Hubble Space Telescope.
Here we present the discovery of SPT0615-JD, a fortuitous z~10
(z_phot=9.9+/-0.6) galaxy candidate stretched into an arc over ~2.5" by the
effects of strong gravitational lensing. Discovered in the Reionization Lensing
Cluster Survey (RELICS) Hubble Treasury program and companion S-RELICS Spitzer
program, this candidate has a lensed H-band magnitude of 25.7+/-0.1 AB mag.
With a magnification of \mu~4-7 estimated from our lens models, the de-lensed
intrinsic magnitude is 27.6+/-0.3 AB mag, and the half-light radius is r_e<0.8
kpc, both consistent with other z>9 candidates. The inferred stellar mass (log
M* /M_Sun=9.7^{+0.7}_{-0.5}) and star formation rate (\log SFR/M_Sun
yr^{-1}=1.3^{+0.2}_{-0.3}) indicate that this candidate is a typical
star-forming galaxy on the z>6 SFR-M* relation. We note that three independent
lens models predict two counterimages, at least one of which should be of a
similar magnitude to the arc, but these counterimages are not yet detected.
Counterimages would not be expected if the arc were at lower redshift. However,
the only spectral energy distributions capable of fitting the Hubble and
Spitzer photometry well at lower redshifts require unphysical combinations of
z~2 galaxy properties. The unprecedented lensed size of this z~10 candidate
offers the potential for the James Webb Space Telescope to study the geometric
and kinematic properties of a galaxy observed 500 Myr after the Big Bang.
Strong gravitational lensing by galaxy clusters magnifies background galaxies, enhancing our ability to discover statistically significant samples of galaxies at z>6, 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 (RELICS), 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 \(z\sim0.4\), 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 \(M=2.51^{+0.15}_{-0.09}\times 10^{14}\)~M\(_{\odot}\). If we extrapolate out to \(r_{500}\), our projected mass density is consistent with the mass inferred from weak lensing and from the Sunyaev-Zel'dovich effect (\(M\sim10^{15}\)~M\(_{\odot}\)). This cluster is lensing a previously reported \(z\sim10\) galaxy, which, if spectroscopically confirmed, will be the highest-redshift strongly lensed galaxy known.
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 z ~ 6 - 8 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 arcmin^2. These clusters were selected to be excellent lenses and we find similar high-redshift sample sizes and magnitude distributions as CLASH. We discover 321 candidate galaxies with photometric redshifts between z ~ 6 to z ~ 8, including extremely bright objects with H-band magnitudes of m_AB ~ 23 mag. As a sample, the observed (lensed) magnitudes of these galaxies are among the brightest known at z> 6, comparable to 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.
Recent observations have revealed the presence of strong CIII emission (EW\(_{\rm{CIII}}>20\) Å) in \(z>6\) galaxies, the origin of which remains unclear. In an effort to understand the nature of ...these line emitters, we have initiated a survey targeting CIII emission in gravitationally-lensed reionization era analogs identified in HST imaging of clusters from the RELICS survey. Here we report initial results on four galaxies selected to have low stellar masses (2-8\(\times\)10\(^7\) M\(_\odot\)) and J\(_{125}\)-band flux excesses indicative of intense OIII+H\(\beta\) emission (EW\(_{\rm{OIII+H\beta}}\)=500-2000 Å), similar to what has been observed at \(z>6\). We detect CIII emission in three of the four sources, with the CIII EW reaching values seen in the reionization era (EW\(_{\rm{CIII}}\simeq 17-22\) Å) in the two sources with the strongest optical line emission (EW\(_{\rm{OIII+H\beta}}\simeq 2000\) Å). We have obtained a Magellan/FIRE near-infrared spectrum of the strongest CIII emitter in our sample, revealing gas that is both metal poor and highly ionized. Using photoionization models, we are able to simultaneously reproduce the intense CIII and optical line emission for extremely young (2-3 Myr) and metal poor (0.06-0.08 Z\(_\odot\)) stellar populations, as would be expected after a substantial upturn in the SFR of a low mass galaxy. The sources in this survey are among the first for which CIII has been used as the primary means of redshift confirmation. We suggest that it should be possible to extend this approach to \(z>6\) with current facilities, using CIII to measure redshifts of objects with IRAC excesses indicating EW\(_{\rm{OIII+H\beta}}\simeq 2000\) Å, providing a method of spectroscopic confirmation independent of Ly\(\alpha\).
The most distant galaxies known are at z~10-11, observed 400-500 Myr after the Big Bang. The few z~10-11 candidates discovered to date have been exceptionally small- barely resolved, if at all, by ...the Hubble Space Telescope. Here we present the discovery of SPT0615-JD, a fortuitous z~10 (z_phot=9.9+/-0.6) galaxy candidate stretched into an arc over ~2.5" by the effects of strong gravitational lensing. Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program and companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 25.7+/-0.1 AB mag. With a magnification of \mu~4-7 estimated from our lens models, the de-lensed intrinsic magnitude is 27.6+/-0.3 AB mag, and the half-light radius is r_e<0.8 kpc, both consistent with other z>9 candidates. The inferred stellar mass (log M* /M_Sun=9.7^{+0.7}_{-0.5}) and star formation rate (\log SFR/M_Sun yr^{-1}=1.3^{+0.2}_{-0.3}) indicate that this candidate is a typical star-forming galaxy on the z>6 SFR-M* relation. We note that three independent lens models predict two counterimages, at least one of which should be of a similar magnitude to the arc, but these counterimages are not yet detected. Counterimages would not be expected if the arc were at lower redshift. However, the only spectral energy distributions capable of fitting the Hubble and Spitzer photometry well at lower redshifts require unphysical combinations of z~2 galaxy properties. The unprecedented lensed size of this z~10 candidate offers the potential for the James Webb Space Telescope to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.
1-E-benzylidene-4,7-dimethylindene (1) is reductively coupled by activated calcium to form two isomers, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2 (trans-rac-2) and ...cis-Ph2C2H2-meso-(η5-4,7-Me2−C9H4)2Ca(THF)2 (cis-meso-2) in an approximately 1:1 ratio. Reaction of the calcium species with FeCl2 produces a mixture of the corresponding trans-rac and cis-meso ferrocenophane species (3) along with another ferrocenophane isomer that is presumed to be either the trans-meso or cis-rac isomer. Thus, the relative geometry of the indenyl rings is not retained entirely during the transfer of the ligand framework from calcium to iron. A complete scrambling of the indenyl ring geometry appears to occur upon transfer of the ligand framework from calcium to zirconium. The results of X-ray crystal structure determinations of 1-E-benzylidene-4,7-dimethylindene, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2, and trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Fe are described.
We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance ...started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and " Angkor," which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum or polarization during the dips and (ii) the multiband photometry of the dips shows differential reddening favoring non-gray extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale << 1 mu m, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.
