Galaxy cluster assembly at z = 0.37

Anthony H. Gonzalez, Kim Vy H. Tran, Michelle N. Conbere, Dennis Zaritsky

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


We present X-ray and spectroscopic confirmation of a cluster assembling from multiple, distinct galaxy groups at z = 0.371. Initially detected in the Las Campanas Distant Cluster Survey, the structure contains at least four X-ray-detected groups that lie within a maximum projected separation of 4 Mpc and within Δv = 550 km s-1 of one another. Using Chandra imaging and wide-field optical spectroscopy, we show that the individual groups lie on the local σ-T relation and derive a total mass of M ≥ 5 × 1014 M for the entire structure. We demonstrate that the groups are gravitationally bound to one another and will merge into a single cluster with about one-third or more the mass of Coma. We also find that although the cluster is in the process of forming, the individual groups already have a higher fraction of passive members than the field. This result indicates that galaxy evolution on group scales is key to developing the early-type galaxies that dominate the cluster population by z ∼ 0.

Original languageEnglish (US)
Pages (from-to)L73-L76
JournalAstrophysical Journal
Issue number2 II
StatePublished - May 10 2005


  • Galaxies: clusters: general
  • Galaxies: evolution
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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