Constraining the Mass of the Emerging Galaxy Cluster SpARCS1049+56 at z = 1.71 with Infrared Weak Lensing

Kyle Finner, M. James Jee, Tracy Webb, Gillian Wilson, Saul Perlmutter, Adam Muzzin, Julie Hlavacek-Larrondo

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7 Citations (Scopus)


In the hierarchical structure formation model of the universe, galaxy clusters are assembled through a series of mergers. Accordingly, it is expected that galaxy clusters in the early universe are actively forming and dynamically young. Located at a high redshift of z = 1.71, SpARCS1049+56 offers a unique look into the galaxy cluster formation process. This cluster has been shown to be rich in cluster galaxies and to have intense star formation. Its high redshift pushes a weak-lensing analysis beyond the regime of the optical spectrum into that of the infrared. Equipped with deep Hubble Space Telescope Wide Field Camera 3 UVIS and IR observations, we present a weak-lensing characterization of SpARCS1049+56. As few IR weak-lensing studies have been performed, we discuss the details of point-spread function modeling and galaxy shape measurement for an IR weak-lensing procedure and the systematics that come with the territory. It will be critical to understand these systematics in future weak-lensing studies in the IR with the next-generation space telescopes such as the James Webb Space Telescope, Euclid, and WFIRST. Through a careful analysis, the mass distribution of this young galaxy cluster is mapped and the convergence peak is detected at a 3.3σ level. The weak-lensing mass of the cluster is estimated to be 3.5 ± 1.2 × 1014 M o˙ and is consistent with the mass derived from a mass-richness scaling relation. This mass is extreme for a cluster at such a high redshift and suggests that SpARCS1049+56 is rare in the standard ΛCDM universe.

Original languageEnglish
Article number10
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2020 Apr 10

Bibliographical note

Funding Information:
Support for the current HST program was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This study is supported by the program Yonsei University Future-Leading Research Initiative. M.J.J. acknowledges support for the current research from the National Research Foundation of Korea under the programs 2017R1A2B2004644 and 2017R1A4A1015178. G.W. acknowledges support from the National Science Foundation through grant AST-1517863, by HST program number GO-15294, and by grant No. 80NSSC17K0019 issued through the NASA Astrophysics Data Analysis Program (ADAP).

Publisher Copyright:
© 2020. The American Astronomical Society. All rights reserved.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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