The z=1.03 Merging Cluster SPT-CL J0356-5337: New Strong Lensing Analysis with HST and MUSE

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Main Authors: Smith, Grace, Mahler, Guillaume, Napier, Kate, Sharon, Keren, Bayliss, Matthew, Benson, Bradford, Bleem, Lindsey, Floyd, Benjamin, Gladders, Michael D., Khullar, Gourav, Schrabback, Tim
Format: Preprint
Published: 2025
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author Smith, Grace
Mahler, Guillaume
Napier, Kate
Sharon, Keren
Bayliss, Matthew
Benson, Bradford
Bleem, Lindsey
Floyd, Benjamin
Gladders, Michael D.
Khullar, Gourav
Schrabback, Tim
author_facet Smith, Grace
Mahler, Guillaume
Napier, Kate
Sharon, Keren
Bayliss, Matthew
Benson, Bradford
Bleem, Lindsey
Floyd, Benjamin
Gladders, Michael D.
Khullar, Gourav
Schrabback, Tim
contents We present a strong lensing analysis and reconstruct the mass distribution of SPT-CL J0356-5337, a galaxy cluster at redshift z = 1.034. Our model supersedes previous models by making use of new multi-band HST data and MUSE spectroscopy. We identify two additional lensed galaxies to inform a more well-constrained model using 12 sets of multiple images in 5 separate lensed sources. The three previously-known sources were spectroscopically confirmed by Mahler et al. (2020) at redshifts of z = 2.363, z = 2.364, and z = 3.048. We measured the spectroscopic redshifts of two of the newly-discovered arcs using MUSE data, at z = 3.0205 and z = 5.3288. We increase the number of cluster member galaxies by a factor of three compared to previous work. We also report the detection of extended Lya emission from several background galaxies. We measure the total projected mass density of the two major sub-cluster components, one dominated by the BCG, and the other by a compact group of luminous red galaxies. We find M_BCG(< 80kpc) = 3.93+0.21-0.14 * 10^13Msun and M_LRG(< 80kpc) = 2.92+0.16 -0.23 * 10^13Msun, yielding a mass ratio of 1.35+0.16 -0.08. The strong lensing constraints offer a robust estimate of the projected mass density regardless of modelling assumptions; allowing more substructure in this line of sight does not change the results or conclusions. Our results corroborate the conclusion that SPT-CL J0356-5337 is dominated by two mass components, and is likely undergoing a major merger on the plane of the sky
format Preprint
id arxiv_https___arxiv_org_abs_2507_07404
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The z=1.03 Merging Cluster SPT-CL J0356-5337: New Strong Lensing Analysis with HST and MUSE
Smith, Grace
Mahler, Guillaume
Napier, Kate
Sharon, Keren
Bayliss, Matthew
Benson, Bradford
Bleem, Lindsey
Floyd, Benjamin
Gladders, Michael D.
Khullar, Gourav
Schrabback, Tim
Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
We present a strong lensing analysis and reconstruct the mass distribution of SPT-CL J0356-5337, a galaxy cluster at redshift z = 1.034. Our model supersedes previous models by making use of new multi-band HST data and MUSE spectroscopy. We identify two additional lensed galaxies to inform a more well-constrained model using 12 sets of multiple images in 5 separate lensed sources. The three previously-known sources were spectroscopically confirmed by Mahler et al. (2020) at redshifts of z = 2.363, z = 2.364, and z = 3.048. We measured the spectroscopic redshifts of two of the newly-discovered arcs using MUSE data, at z = 3.0205 and z = 5.3288. We increase the number of cluster member galaxies by a factor of three compared to previous work. We also report the detection of extended Lya emission from several background galaxies. We measure the total projected mass density of the two major sub-cluster components, one dominated by the BCG, and the other by a compact group of luminous red galaxies. We find M_BCG(< 80kpc) = 3.93+0.21-0.14 * 10^13Msun and M_LRG(< 80kpc) = 2.92+0.16 -0.23 * 10^13Msun, yielding a mass ratio of 1.35+0.16 -0.08. The strong lensing constraints offer a robust estimate of the projected mass density regardless of modelling assumptions; allowing more substructure in this line of sight does not change the results or conclusions. Our results corroborate the conclusion that SPT-CL J0356-5337 is dominated by two mass components, and is likely undergoing a major merger on the plane of the sky
title The z=1.03 Merging Cluster SPT-CL J0356-5337: New Strong Lensing Analysis with HST and MUSE
topic Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2507.07404