Witnessing the hierarchical assembly of the brightest cluster galaxy in a cluster at z = 1.26

Toru Yamada, Yohei Koyama, Fumiaki Nakata, Masaru Kajisawa, Ichi Tanaka, Tadayuki Kodama, Sadanori Okamura, Roberto De Propris

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


We have obtained a new high-resolution K′-band image of the central region of the rich X-ray cluster RX J0848.9+4452 at z = 1.26. We found that the brightest cluster galaxy (BCG) in the cluster is clearly separated into two distinct objects. Whereas the optical to near-infrared colors of the objects are consistent with the predictions of passive evolution models for galaxies formed at high redshift, the luminosities of the two galaxies are both considerably fainter than predicted by passive evolution of BCGs in low- and intermediate-redshift clusters. We argue that this is evidence of an ongoing merger of normal cluster elliptical galaxies to form the dominant galaxy in the core of RX J0848.9+4452. The two galaxies appear to point toward the nearby cluster CIG J0848+4453 and are aligned with the outer X-ray contour of their parent cluster, supporting a model of BCG formation by collimated infall along the surrounding large-scale structure.

Original languageEnglish
Pages (from-to)L89-L92
JournalAstrophysical Journal
Issue number2 II
Publication statusPublished - 2002 Oct 1


  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Galaxies: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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