Quiescent galaxies in a virialized cluster at redshift 2: evidence for accelerated size growth

E. Noordeh*, R. E. A. Canning, J. P. Willis, S. W. Allen, A. Mantz, S. A. Stanford, G. Brammer

*Corresponding author for this work

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We present an analysis of the galaxy population in XLSSC 122, an X-ray selected, virializedcluster at redshift 𝑧 = 1.98. We utilize Hubble Space Telescope (HST)Wide Field Camera 3 (WFC3) photometry to characterize the activity andmorphology of spectroscopically confirmed cluster members. The quiescent fraction is found to be 88+4−20 per cent within 0.5𝑟500, significantly enhanced over the field value of 20+2−2per cent at 𝑧 ∼ 2. We find an excess of 'bulge-like' quiescent cluster members with Sérsic index 𝑛 > 2relative to the field. These galaxies are found to be larger than their field counterparts at 99.6per cent confidence, being on average 63+31−24 per cent larger at a fixed mass of M⋆ = 5 × 1010 M. This suggests that these cluster member galaxies have experienced an accelerated size evolution relative to the field at 𝑧 > 2. We discuss minor mergers as a possible mechanism underlying this disproportionate size growth.
Original languageEnglish
Pages (from-to)5272-5280
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date2 Sept 2021
Publication statusPublished - 1 Nov 2021


  • galaxies: clusters: general
  • galaxies: evolution
  • galaxies: fundamental parameters
  • galaxies: high-redshift
  • galaxies: stellar content
  • galaxies: structure


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