An IR-Selected Galaxy Cluster at ζ=1.27
Abstract
We report the discovery of a galaxy cluster at ζ = 1.27. ClG J0848+4453 was found in a near-IR field survey as a high density region of objects with very red J-K colors. Optical spectroscopy of a limited number of 24≤R≤25 objects in the area shows that 6 galaxies within a 90 arcsec (0.49h-1100 Mpc, q0=0.1) diameter region lie at ζ=1.273±0.002. Most of these 6 member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift. An additional 2 galaxies located 2 arcmin from the cluster center are also at ζ=1.27. Using all 8 of these spectroscopic members, we estimate the velocity dispersion σ=700±180 km s1-1, which is similar to that of Abell richness class R=1 clusters in the present epoch. A deep ROSAT/PSPC observation detects X-ray emission at the 4.50σ level coincident with the nominal cluster center. Assuming that the X-ray flux is emitted by hot gas trapped in the potential well of a collapsed system (no AGN are known to exist in the area), the resulting X-ray luminosity in the rest frame 0.1-2.4 keV band of Lχ=1.5×1044 ergs s-1 suggests the presence of a moderately massive system. ClG J0848+4453 is the highest redshift cluster found in a field survey.
- Publication:
-
The Astronomical Journal
- Pub Date:
- December 1997
- DOI:
- arXiv:
- arXiv:astro-ph/9709057
- Bibcode:
- 1997AJ....114.2232S
- Keywords:
-
- GALAXIES: CLUSTERS: GENERAL;
- INFRARED: GALAXIES;
- GALAXIES: DISTANCES AND REDSHIFTS;
- Astrophysics
- E-Print:
- Accepted for publication in The Astronomical Journal