RELICS: Reionization Lensing Cluster Survey

Abstract

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 0.4-1.7µm and 3.0-5.0µm, 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 highredshift 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 spatially-resolved distant 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 Cycle 1 call for proposals.

ALMA 1.3 mm Survey of Lensed Submillimeter Galaxies Selected by Herschel: Discovery of Spatially Extended SMGs and Implications

“…For a number of clusters, we also included other ancillary data to improve the quality of analysis, mainly for the optical SED fitting. This provides more accurate extinction and stellarmass estimates, compared with IRAC-only analyses: MACS J0553.4-3342-this cluster was observed with the HST treasury program RELICS (Coe et al 2019), and therefore, we used its seven-band HST data for photometry and SED fitting (ACS/F435W, F606W, F814W, and WFC3-IR/F110W, F125W, F140W, F160W). MACS J1115.8 + 0129-this cluster was observed with the HST treasury program CLASH (Postman et al 2012), and therefore, its nine-band HST data were utilized (ACS/F435W, F606W, F775W, F814W, WFC3-IR/F105W, F110W, F125W, F140W, F160W).…”

ALMA Lensing Cluster Survey: a strongly lensed multiply imaged dusty system at z ≥ 6

“…A search for an ultraviolet (UV) rest-frame counterpart for this source was undertaken on deep HST images from the RELICS survey with a search radius of 2 . The data reduction of this dataset is described in Coe et al (2019). Photometric catalogues were built using version 2.19.5 of SExtractor Bertin & Arnouts (1996) in dual image mode on psf matched images.…”

“…With current facilities, the only way to characterise the physical properties of this sub-luminous population is to use the magnification afforded by gravitational lensing (for a review see Kneib & Natarajan 2011). Although several surveys have harnessed the lensing power of foreground clusters, such as the Cluster Lensing And Supernova survey with Hubble (CLASH ; Postman et al 2012), the Hubble Frontier Fields (Lotz et al 2017) and most recently REionization LensIng Cluster Survey (RELICS ; Coe et al 2019), the effective surface area explored for the most highlymagnified background sources remains small. As a consequence, very few high-redshift sources ( ≥6) with magnifications ≥10 have so far been found (e.g., Coe et al 2013, Salmon et al 2018.…”

ALMA Lensing Cluster Survey: An ALMA Galaxy Signposting a MUSE Galaxy Group at z = 4.3 Behind “El Gordo”

“…Lensing fields are excellent systems to study high-redshift galaxies to fainter limits than what is typically possible with current telescopes. Several observational campaigns (Postman et al 2012;Lotz et al 2017;Coe et al 2019) have targeted lensing clusters with major observatories, such as the Hubble Space Telescope (HST), enabling a large number of studies of the cluster members, as well as their magnified background sources.…”