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The Brightest UV-selected Galaxies in Protoclusters at z ∼ 4: Ancestors of Brightest Cluster Galaxies?

  • Ito, K
  • Kashikawa, N
  • Toshikawa, J
  • Overzier, R
  • Tanaka, M
  • Kubo, M
  • Shibuya, T
  • Ishikawa, S
  • Onoue, M
  • Uchiyama, H
  • Liang, Y
  • Higuchi, R
  • Martin, CL
  • Lee, CH
  • Komiyama, Y
  • Huang, S
Publication Date
Jun 10, 2019
eScholarship - University of California
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© 2019. The American Astronomical Society. All rights reserved. We present the results of a survey of the brightest UV-selected galaxies in protoclusters. These proto-brightest cluster galaxy (proto-BCG) candidates are drawn from 179 overdense regions of g-dropout galaxies at z ∼ 4 from the Hyper Suprime-Cam Subaru Strategic Program identified previously as good protocluster candidates. This study is the first to extend the systematic study of the progenitors of BCGs from z ∼ 2 to z ∼ 4. We carefully remove possible contaminants from foreground galaxies and, for each structure, select the brightest galaxy that is at least 1 mag brighter than the fifth-brightest galaxy. We select 63 proto-BCG candidates and compare their properties with those of galaxies in the field and those of other galaxies in overdense structures. The proto-BCG candidates and their surrounding galaxies have different rest-UV color (i - z) distributions to field galaxies and other galaxies in protoclusters that do not host proto-BCGs. In addition, galaxies surrounding proto-BCGs are brighter than those in protoclusters without proto-BCGs. The image stacking analysis reveals that the average effective radius of proto-BCGs is ∼28% larger than that of field galaxies. The i - z color differences suggest that proto-BCGs and their surrounding galaxies are dustier than other galaxies at z ∼ 4. These results suggest that specific environmental effects or assembly biases have already emerged in some protoclusters as early as z ∼ 4, and we suggest that proto-BCGs have different star formation histories than other galaxies in the same epoch.

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