Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The Formation Epoch of Massive Stellar Systems
Abstract
We present spectroscopic evidence from the Gemini Deep Deep Survey (GDDS) for a significant population of color-selected red galaxies at 1.3 < z < 2.2 whose integrated light is dominated by evolved stars. Unlike radio-selected objects, the z > 1.5 old galaxies have a sky density > 0.1 per sq. arcmin. Conservative age estimates for 20 galaxies with z > 1.3; <z> = 1.49, give a median age of 1.2 Gyr and <z_f> = 2.4. One quarter of the galaxies have inferred z_f > 4. Models restricted to abundances less than or equal to solar give median ages and z_f of 2.3 Gyr and 3.3, respectively. These galaxies are among the most massive and contribute approximately 50% of the stellar mass density at 1 < z < 2. The derived ages and most probable star formation histories suggest a high star-formation-rate (300-500 solar masses per year) phase in the progenitor population. We argue that most of the red galaxies are not descendants of the typical z=3 Lyman break galaxies. Galaxies associated with luminous sub-mm sources have the requisite star formation rates to be the progenitor population. Our results point toward early and rapid formation for a significant fraction of present day massive galaxies.
Cite
@article{arxiv.astro-ph/0408367,
title = {Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The Formation Epoch of Massive Stellar Systems},
author = {Patrick J. McCarthy and Damien Le Borgne and David Crampton and Hsiao-Wen Chen and Roberto G. Abraham and Karl Glazebrook and Sandra Savaglio and Raymond G. Carlberg and Ronald O. Marzke and Kathy Roth and Inger Jorgensen and Isobel Hook and Richard Murowinski and Stephanie Juneau},
journal= {arXiv preprint arXiv:astro-ph/0408367},
year = {2009}
}
Comments
12 pages, 2 figures, 1 table, Accepted for publication, ApJ Letters