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arXiv · astro-ph/0408367

Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The Formation Epoch of Massive Stellar Systems

Patrick J. McCarthy·Damien Le Borgne·David Crampton·Hsiao-Wen Chen·Roberto G. Abraham·Karl Glazebrook·Sandra Savaglio·Raymond G. Carlberg·Ronald O. Marzke·Kathy Roth·Inger Jorgensen·Isobel Hook·Richard Murowinski·Stephanie Juneau
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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; = 1.49, give a median age of 1.2 Gyr and = 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.

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Patrick J. McCarthy, Damien Le Borgne, David Crampton, Hsiao-Wen Chen, Roberto G. Abraham, Karl Glazebrook, Sandra Savaglio, Raymond G. Carlberg, Ronald O. Marzke, Kathy Roth, Inger Jorgensen, Isobel Hook, Richard Murowinski, Stephanie Juneau. 2004-08-19. Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The Formation Epoch of Massive Stellar Systems. https://doi.org/10.1086/425306

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