RELICS: Strong Lensing analysis of the galaxy clusters Abell S295, Abell 697, MACS J0025.4-1222, and MACS J0159.8-0849

TL;DR

This paper presents strong lensing models for four galaxy clusters, revealing their mass distributions, merger states, and lensing strengths, and includes spectroscopic confirmation of a high-redshift galaxy behind one cluster.

Contribution

First published mass models for Abell S295 and MACS J0159.8-0849, with improved models for Abell 697 and MACS J0025.4-1222, and analysis of their lensing properties and merger scenarios.

Findings

Bimodal mass distribution in MACS J0025.4-1222 and Abell S295 supports merger scenarios.

Updated model for MACS J0025.4-1222 indicates smaller critical area.

Three clusters have lensing strengths comparable to Hubble Frontier Fields clusters.

Abstract

We present a strong-lensing analysis of four massive galaxy clusters imaged with the Hubble Space Telescope in the Reionization Lensing Cluster Survey. We use a Light-Traces-Mass technique to uncover sets of multiply images and constrain the mass distribution of the clusters. These mass models are the first published for Abell S295 and MACS J0159.8-0849, and are improvements over previous models for Abell 697 and MACS J0025.4-1222. Our analysis for MACS J0025.4-1222 and Abell S295 shows a bimodal mass distribution supporting the merger scenarios proposed for these clusters. The updated model for MACS J0025.4-1222 suggests a substantially smaller critical area than previously estimated. For MACS J0159.8-0849 and Abell 697 we find a single peak and relatively regular morphology, revealing fairly relaxed clusters. Despite being less prominent lenses, three of these clusters seem to have lensing strengths, i.e. cumulative area above certain magnification, similar to the Hubble Frontier Fields clusters (e.g., A($\mu>5$) $\sim 1-3$ arcmin$^2$, A($\mu>10$) $\sim 0.5-1.5$ arcmin$^2$), which in part can be attributed to their merging configurations. We make our lens models publicly available through the Mikulski Archive for Space Telescopes. Finally, using Gemini-N/GMOS spectroscopic observations we detect a single emission line from a high-redshift $J_{125}\simeq25.7$ galaxy candidate lensed by Abell 697. While we cannot rule out a lower-redshift solution, we interpret the line as Ly$\alpha$ at $z=5.800\pm 0.001$, in agreement with its photometric redshift and dropout nature. Within this scenario we measure a Ly$\alpha$ rest-frame equivalent width of $52\pm22$ \AA, and an observed Gaussian width of $117\pm 15$ km/s.