A Group of Galaxies at Redshift 2.38

Authors

Paul J. Francis, University of Melbourne
Bruce E. Woodgate, Association of Universities for Research in Astronomy, Inc. (AURA)
Stephen J. Warren, NASA Goddard Space Flight Center
Palle Møller, Imperial College London
Margaret Mazzolini, Space Telescope Science Institute
Andrew J. Bunker, University of Oxford
James D. Lowenthal, University of California, Santa CruzFollow
Ted B. Williams, Rutgers University–New Brunswick
Takeo Minezaki, The University of Tokyo
Yukiyasu Kobayashi, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
Yuzuru Yoshii, The University of Tokyo

Document Type

Article

Publication Date

1-1-1996

Publication Title

Astrophysical Journal

Abstract

We report the discovery of a group of galaxies at redshift 2.38. We imaged ∼ 10% of a claimed supercluster of QSO absorption lines at z = 2.38. In this small field (2′ radius), we detect two Lyα-emitting galaxies. The discovery of two such galaxies in our tiny field supports Francis & Hewett's interpretation of the absorption-line supercluster as a high-redshift Great Wall. One of the Lyα galaxies lies 22″ from a background QSO and may be associated with a multicomponent Lyα absorption complex seen in the QSO spectrum. This galaxy has an extended (∼50 kpc), lumpy Lyα morphology surrounding a compact, IR-bright nucleus. The nucleus shows a pronounced break in its optical-UV colors at ∼4000 Å (rest frame), consistent with a stellar population of mass ∼7 × 10 M , an age of greater than 500 Myr, and little ongoing star formation. C iv emission is detected, which suggests that a concealed active galactic nucleus is present. The Lyα emission is redshifted by ∼490 km s with respect to the C IV emission, probably because of absorption. Extended Hα emission is also detected; the ratio of Lyα flux to Hα is abnormally low (∼0.7), probable evidence for extended dust. This galaxy is surrounded by a number of very red (B -K > 5 mag) objects, some of which have colors that suggest that they too are at z = 2.38. We hypothesize that this galaxy, its neighbors, and a surrounding lumpy gas cloud may be a giant elliptical galaxy in the process of bottom-up formation.

Keywords

Galaxies: Clusters: Individual (2139-4434), Galaxies: Distances and redshifts

Volume

457

Issue

2 PART I

First Page

490

Last Page

499

DOI

10.1086/176747

ISSN

0004637X

Comments

Peer reviewed accepted manuscript.

Recommended Citation

Francis, Paul J.; Woodgate, Bruce E.; Warren, Stephen J.; Møller, Palle; Mazzolini, Margaret; Bunker, Andrew J.; Lowenthal, James D.; Williams, Ted B.; Minezaki, Takeo; Kobayashi, Yukiyasu; and Yoshii, Yuzuru, "A Group of Galaxies at Redshift 2.38" (1996). Astronomy: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/ast_facpubs/54