RCS2 J232727.6-020437: An Efficient Cosmic Telescope at $z=0.6986$

Abstract

We present a detailed gravitational lens model of the galaxy cluster RCS2 J232727.6-020437. Due to cosmological dimming of cluster members and ICL, its high redshift ($z=0.6986$) makes it ideal for studying background galaxies. Using new ACS and WFC3/IR HST data, we identify 16 multiple images. From MOSFIRE follow up, we identify a strong emission line in the spectrum of one multiple image, likely confirming the redshift of that system to $z=2.083$. With a highly magnified ($\mu \gtrsim 2$) source plane area of $\sim 0.7$ arcmin${}^2$ at $z=7$, RCS2 J232727.6-020437 has a lensing efficiency comparable to the Hubble Frontier Fields clusters. We discover four highly magnified $z\sim 7$ candidate Lyman-break galaxies behind the cluster, one of which may be multiply-imaged. Correcting for magnification, we find that all four galaxies are fainter than $0.5L_{\star }$. One candidate is detected at $>10\sigma$ in both Spitzer/IRAC [3.6] and [4.5] channels. A spectroscopic follow-up with MOSFIRE does not result in the detection of the Lyman-alpha emission line from any of the four candidates. From the MOSFIRE spectra we place median upper limits on the Lyman-alpha flux of $5-14\times 10^{-19}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}$ ($5\sigma$).

14 pages, 9 figures, submitted to ApJ on 3/06/2015

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Cited by in corpus (8)

• The Frontier Fields Lens Modeling Comparison Project
• Constraining the neutral fraction of hydrogen in the IGM at redshift 7.5
• The Atacama Cosmology Telescope: The Two-Season ACTPol Sunyaev-Zel'dovich Effect Selected Cluster Catalog
• An Atlas of MUSE Observations towards Twelve Massive Lensing Clusters
• The Grism Lens-Amplified Survey from Space (GLASS). III. A census of Lyα Emission at $z\gtrsim$7 from HST Spectroscopy
• Spitzer UltRa Faint SUrvey Program (SURFS UP). II. IRAC-Detected Lyman-Break Galaxies at 6 < z < 10 Behind Strong-Lensing Clusters
• RELICS: A Strong Lens Model for SPT-CLJ0615-5746, a z=0.972 Cluster
• Precise weak lensing constraints from deep high-resolution $K_{\mathrm{s}}$ images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2$J$232727.7$-$020437 at $z=0.70$