Clustering around the radio-galaxy MRC0316-257 at z=3.14

O. Le Fevre; J. M. Deltorn; D. Crampton; M. Dickinson

doi:10.1086/310319

paper

Clustering around the radio-galaxy MRC0316-257 at z=3.14

arXiv:astro-ph/9609020 · doi:10.1086/310319

Abstract

We report here the spectroscopic identification of galaxies in the neighborhood of the radio-galaxy MRC0316-257, at a redshift $z \sim 3.14$ . Candidate cluster galaxies were selected from deep V and I images combined with narrow band imaging at the wavelength of redshifted Ly $α$ . Follow-up multi-slit spectroscopy has allowed confirmation of the redshift of the radio-galaxy, $z = 3.1420 \pm 0.0020$ , and identification of two associated galaxies at redshifts $z = 3.1378 \pm 0.0028$ and $z = 3.1351 \pm 0.0028$ respectively. The first galaxy is 0.3 $h_{50}^{- 1}$ Mpc from the radio-galaxy, is resolved with an intrinsic size $11.6 \pm h_{50}^{- 1}$ kpc, and shows $L y α$ in emission with rest $W_{L y α} = 55 \pm 14$ Å. In addition, its extremely blue $V - I$ color might possibly indicate a proto-galaxy forming a first generation of stars in a low dust medium. The second galaxy is 1.3 $h_{50}^{- 1}$ Mpc away from the radio-galaxy, is marginally resolved and, in addition to Ly $α$ in emission, shows CIV in emission with a broad component indicating the contribution from an AGN. The comoving density of galaxies with $V < 23.8$ and a $L y α$ flux $> 1 0^{- 16}$ ergcm $^{- 2}$ sec $^{- 1}$ in the vicinity of MRC0316-257 is $\sim 2.5 \times 1 0^{- 3} h_{50}^{3} M p c^{- 3}$ , significantly higher than the expected background density of field galaxies with similar properties, and might indicate a rich cluster or proto-cluster environment.

10 pages, 2 figures (postscript), figure 1 available upon request to [email protected]. To appear in the Astrophysical Journal Letters

Clustering around the radio-galaxy MRC0316-257 at z=3.14

Abstract

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