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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 276829.0, MPI für Astronomie / Publikationen_mpia
IRAC mid-infrared imaging of the Hubble Deep Field-South: Star formation histories and stellar masses of red galaxies at z>2
Authors:Labbé, Ivo; Huang, Jiasheng; Franx, Marijn; Rudnick, Gregory; Barmby, Pauline; Daddi, Emanuele; van Dokkum, Pieter G.; Fazio, Giovanni G.; Schreiber, Natascha M. Förster; Moorwood, Alan F. M.; Rix, Hans-Walter; Röttgering, Huub; Trujillo, Ignacio; van der Werf, Paul
Date of Publication (YYYY-MM-DD):2005
Title of Journal:The Astrophysical Journal
Journal Abbrev.:The Astrophysical Journal
Start Page:L81
End Page:L84
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We present deep 3.6-8 mum imaging of the Hubble Deep Field-South with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We study distant red galaxies (DRGs) at z>2 selected by Js-Ks>2.3 and compare them with a sample of Lyman break galaxies (LBGs) at z=2-3. The observed UV-to-8 mum spectral energy distributions are fitted with stellar population models to constrain star formation histories and derive stellar masses. We find that 70% of the DRGs are best described by dust-reddened star-forming models and 30% are very well fitted with old and ``dead'' models. Using only the I-Ks and Ks-4.5 mum colors, we can effectively separate the two groups. The dead systems are among the most massive at z~2.5 (mean stellar mass <M*>= 0.8_1011 Msolar) and likely formed most of their stellar mass at z>5. To a limit of 0.5_1011 Msolar, their number density is ~10 times lower than that of local early- type galaxies. Furthermore, we use the IRAC photometry to derive rest-frame near- infrared J, H, and K fluxes. The DRGs and LBGs together show a large variation (a factor of 6) in the rest-frame K-band mass-to-light ratios (M/LK), implying that even a Spitzer 8 mum-selected sample would be very different from a mass-selected sample. The average M/LK of the DRGs is about 3 times higher than that of the LBGs, and DRGs dominate the high-mass end. The M/LK values and ages of the two samples appear to correlate with derived stellar mass, with the most massive galaxies being the oldest and having the highest mass-to-light ratios, similar to what is found in the low-redshift universe.
Free Keywords:Galaxies: Evolution; Galaxies: High-Redshift; Infrared: Galaxies
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/cgi-bin/nph- bib_query?b... [ID No:1]
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