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Published 2006 | Published
Book Section - Chapter Open

High-z Galaxies Detected by the GOODS IRAC Observations in the HST Ultra Deep Field

Abstract

The first epoch of Infrared Array Camera (IRAC) observations of the Great Observatories Origins Deep Survey (GOODS) Spitzer Legacy Program have successfully detected galaxies out to z ≈ 6, allowing us to study the rest-frame optical properties of galaxies at these very high redshifts. We investigate such properties of a collection of Lyman-break galaxy candidates at z=5–6 in the Hubble Ultra Deep Field (HUDF), several of which have spectroscopic confirmations. We find that the bulk of the rest-frame optical fluxes of these IRAC-identified high-redshift galaxies are best fitted by well-evolved stellar populations with stellar masses of a few ×10^(10) M_☉ and ages of a few hundred million years. This implies that massive galaxies already existed when the universe was only ~0.9 Gyr old, and that the formation redshifts of their evolved components could be as early as at z_f ≈ 10–11. These evolved populations can be well explained by a single stellar population, suggesting that they were formed through a sudden on-set rather than a prolonged process. Their colors are consistent with solar metallicity, suggesting that they might already have been significantly polluted by metals.

Additional Information

© 2006 Astronomical Society of the Pacific. We acknowledge the support provided by NASA through Contract Number 1224666 issued by JPL/Caltech under NASA contract 1407.

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August 19, 2023
Modified:
January 13, 2024