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arXiv · 1910.14006

Strong Lensing Model of SPT-CLJ0356-5337, a Major Merger Candidate at Redshift 1.0359

Guillaume Mahler·Keren Sharon·Michael D. Gladders·Lindsey Bleem·Matthew B. Bayliss·Michael S. Calzadilla·Benjamin Floyd·Gourav Khullar·Michael McDonald·Juan D. Remolina Gonzàlez·Tim Schrabback·Antony A. Stark·Jan Luca van den Busch
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Abstract

We present an analysis of the mass distribution inferred from strong lensing by SPT-CL J0356-5337, a cluster of galaxies at redshift z = 1.0359 revealed in the follow-up of the SPT-SZ clusters. The cluster has an Einstein radius of Erad=14 for a source at z = 3 and a mass within 500 kpc of M_500kpc = 4.0+-0.8x10^14Msol. Our spectroscopic identification of three multiply-imaged systems (z = 2.363, z = 2.364, and z = 3.048), combined with HST F606W-band imaging allows us to build a strong lensing model for this cluster with an rms of <0.3'' between the predicted and measured positions of the multiple images. Our modeling reveals a two-component mass distribution in the cluster. One mass component is dominated by the brightest cluster galaxy and the other component, separated by ~170 kpc, contains a group of eight red elliptical galaxies confined in a ~9'' (~70 kpc) diameter circle. We estimate the mass ratio between the two components to be between 1:1.25 and 1:1.58. In addition, spectroscopic data reveal that these two near-equal mass cores have only a small velocity difference of 300 km/s between the two components. This small radial velocity difference suggests that most of the relative velocity takes place in the plane of the sky, and implies that SPT-CL J0356-5337 is a major merger with a small impact parameter seen face-on. We also assess the relative contributions of galaxy-scale halos to the overall mass of the core of the cluster and find that within 800 kpc from the brightest cluster galaxy about 27% of the total mass can be attributed to visible and dark matter associated with galaxies, whereas only 73% of the total mass in the core comes from cluster-scale dark matter halos.

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Guillaume Mahler, Keren Sharon, Michael D. Gladders, Lindsey Bleem, Matthew B. Bayliss, Michael S. Calzadilla, Benjamin Floyd, Gourav Khullar, Michael McDonald, Juan D. Remolina Gonzàlez, Tim Schrabback, Antony A. Stark, Jan Luca van den Busch. 2019-10-30. Strong Lensing Model of SPT-CLJ0356-5337, a Major Merger Candidate at Redshift 1.0359. https://doi.org/10.3847/1538-4357%2Fab886b

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