Clustering around the Radio Galaxy MRC 0316-257 at Z = 3.14
Abstract
We report the spectroscopic identification of galaxies in the neighborhood of the radio galaxy MRC 0316-257, at a redshift z ~ 3.14. Candidate cluster galaxies were selected from deep V and I images combined with narrowband imaging at the wavelength of redshifted Ly alpha . Follow-up multislit spectroscopy has allowed confirmation of the redshift of the radio galaxy, z = 3.1420 +/- 0.0020, and identification of two associated galaxies at redshifts z = 3.1378 +/- 0.0028 and z = 3.1351 +/- 0.0028. The first is 0.3 h ^{-1}50 Mpc from the radio galaxy, is resolved with an intrinsic size of 11.6 +/- 1.1 h ^{-1}50 kpc, and shows Ly alpha in emission with rest WLy alpha = 55 +/- 14 A. In addition, its extremely blue V - I color might indicate a protogalaxy forming a first generation of stars in a low-dust medium. The second galaxy is 1.3 h ^{-1}50 Mpc from the radio galaxy, is marginally resolved, and, in addition to Ly alpha in emission, shows C IV in emission with a broad component that indicates the contribution from an active galactic nucleus. The comoving density of galaxies with V < 23.8 and Ly alpha flux greater than 10-16 ergs cm-2 s-1 in the vicinity of MRC 0316-257 is ~2.5 x 10-3 h 350 Mpc-3, significantly higher than the expected background density of field galaxies with similar properties, and may indicate a rich cluster or protocluster environment. These observations indicate that the environment of high-redshift radio galaxies may provide significant numbers of galaxies with which to study the early stages of cluster formation and galaxy evolution.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1996
- DOI:
- 10.1086/310319
- arXiv:
- arXiv:astro-ph/9609020
- Bibcode:
- 1996ApJ...471L..11L
- Keywords:
-
- COSMOLOGY: OBSERVATIONS;
- COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE;
- GALAXIES: CLUSTERS: GENERAL;
- GALAXIES: FORMATION;
- GALAXIES: EVOLUTION;
- Astrophysics
- E-Print:
- 10 pages, 2 figures (postscript), figure 1 available upon request to lefevre@daec.obspm.fr. To appear in the Astrophysical Journal Letters