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Paper: High-z Galaxies Detected by the GOODS IRAC Observations in the HST Ultra Deep Field
Volume: 357, The Spitzer Space Telescope: New Views of the Cosmos
Page: 288
Authors: Yan, H.; Dickinson, M.; Giavalisco, M.; Ferguson, H.C.; Stern, D.; Eisenhardt, P.R.M.; Chary, R.; Casertano, S.; Conselice, C.J.; Papovich, C.; Reach, W.T.; Moustakas, L.A.
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 ×1010MSolar 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 zf ≈ 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.
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