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Faculty of Graduate Studies

Bryn Lonsbrough

  • BSc/BA (University of California Santa Cruz, 2022)
Notice of the Final Oral Examination for the Degree of Master of Science

Topic

An Investigation of the Outskirts of the Galaxy Cluster XLSSC122

Department of Physics and Astronomy

Date & location

  • Monday, August 11, 2025
  • 9:00 A.M.
  • Clearihue Building, Room B017

Examining Committee

Supervisory Committee

  • Dr. Jon Willis, Department of Physics and Astronomy, ßÉßɱ¬ÁÏ (Supervisor)
  • Dr. Patrick Côté, Department of Physics and Astronomy, UVic (Member)

External Examiner

  • Dr. Tracy Webb, Department of Physics, McGill University

Chair of Oral Examination

  • Dr. Tao Lu, Department of Electrical and Computer Engineering, UVic

Abstract

I investigate the redshift 1.98 galaxy cluster XLSSC 122 using the Hubble Space Telescope (HST) from the core of the cluster out to 3Mpc, a scale equivalent to 10 times the R500 = 295 kpc radius. I present an expanded photometric and spectroscopic catalogue of the cluster, bringing the total number of spectroscopically classified member galaxies to 74, with 35 new member galaxies added in the outer regions of the cluster. I compute the radial galaxy number density profiles in the cluster, and observe no clear evidence of infalling groups or cosmic filaments. I observe a clear bimodal colour relation in member galaxies, with an increasing number of red galaxies approaching the cluster centre. This red fraction enhancement, as well as the coincident appearance of post-starburst galaxies, indicates a rapid cessation of star formation as galaxies enter the cluster. Our finding of post-starburst features and cluster and galaxy properties is not inconsistent with ram pressure stripping at or near the virial radius of the cluster.

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