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Morphological Evolution in High‐Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

Morphological Evolution in High‐Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

Authors :
Hyron Spinrad
Wil van Breugel
James R. Graham
Daniel Stern
Spencer A. Stanford
Source :
The Astrophysical Journal. 502:614-629
Publication Year :
1998
Publisher :
American Astronomical Society, 1998.

Abstract

We present deep near-IR images of high redshift radio galaxies obtained with NIRC on the Keck I telescope. In most cases, the near-IR data sample rest wavelengths at ~4000 Angstroms, free of strong emission lines. At z > 3, the rest frame optical morphologies generally have faint, large-scale emission surrounding multiple components of ~10 kpc size. The brightest of the small knots are often aligned with the radio structures. At z < 3, the morphologies change dramatically, showing single, compact structures without radio-aligned features. The sizes and luminosities of the individual components in the z > 3 radio galaxies are similar to those of the radio-quiet star-forming galaxies discovered at z ~ 3 by the Lyman dropout technique. The rest frame optical colors of the z > 3 radio galaxies are consistent with models in which recent star formation dominates the observed IR light, and in one case (4C 41.17) we have direct spectroscopic evidence for massive star formation (Dey et al. 1997a). Our results suggest that the z > 3 radio galaxies evolve into very massive elliptical galaxies at 2 < z < 3, in qualitative agreement with the hierarchical model of galaxy formation. We also discuss the Hubble diagram of radio galaxies, the possibility of a radio power dependence in the K-z relation, and the implications for radio galaxy formation.<br />Accepted for publication in The Astrophysical Journal; 34 pages including 8 postscript figures; plates 1-4 may be obtained from ftp://bigz.berkeley.edu/pub/nirc/

Details

ISSN :
15384357 and 0004637X
Volume :
502
Database :
OpenAIRE
Journal :
The Astrophysical Journal
Accession number :
edsair.doi.dedup.....c4b2dffee4c7107dbb9fcb27ff2cc741
Full Text :
https://doi.org/10.1086/305925