ERO R1 in the field of Cl 0939+4713: Evidence for an S0-like galaxy at z ∼ 1.5

Masanori Iye, Kazuhiro Shimasaku, Satoshi Miyazaki, Chris Simpson, Masatoshi Imanishi, Nobunari Kashikawa, Tadayuki Kodama, Masashi Chiba, Yoshihiko Saito, Miwa Goto, Fumihide Iwamuro, Naoto Kobayashi, Sadanori Okamura, Hiroshi Terada

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We present further observations of the extremely red object ERO J094258+4659.2, identified earlier by lye et al. as ERO R1 in their deep images of the cluster A851. We estimate its redshift independently by eight-band photometric redshift determination and cross-correlation of a new H-band spectrum with the optical spectra of local E/S0 galaxies and conclude that it lies at z ∼ 1.5. Although its colors are consistent with both an elliptical galaxy and an S0 galaxy at that redshift, its elongated shape and exponential luminosity profile suggest the presence of an evolved stellar disk component. We rule out the possibility that these properties are strongly influenced by gravitational lensing by the foreground cluster and therefore conclude that this object is more likely to be an S0-like galaxy rather than a lensed elliptical. The H-band spectrum does not show strong Hα emission, and the star formation rate therefore appears to be very modest. The presence of such a galaxy with an apparently relaxed disk of stars at this high redshift provides a new and strong constraint on theoretical models that aim to explain the formation and evolution of galaxies.

Original languageEnglish
Pages (from-to)770-777
Number of pages8
JournalAstrophysical Journal
Issue number2 I
Publication statusPublished - 2003 Jun 20
Externally publishedYes


  • Galaxies: clusters: individual (A851)
  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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