Spitzer observations of red galaxies: Implication for high-redshift star formation
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
My colleagues and I identified distant red galaxies (DRGs) with J - K s > 2.3 in the southern Great Observatories Origins Deep Surveys (GOODS-S) field. These galaxies reside at z 1-3.5, (z 2.2) and based on their ACS (0.4-1 m), ISAAC (1-2.2 m), and IRAC (3-8 m) photometry, they typically have stellar masses M 10 11 M . Interestingly, more than 50% of these objects have 24 m flux densities 50 Jy. Attributing the IR emission to star-formation implies star-formation rates (SFRs) of 100-1000 M yr -1. As a result, galaxies with M 10 11 M have specific SFRs equal to or exceeding the global value at z 1.5-3. In contrast, galaxies with M 10 11 M at z 0.3-0.75 have specific SFRs less than the global average, and more than an order of magnitude lower than that for massive DRGs at z 1.5-3. Thus, the bulk of star formation in massive galaxies is largely complete by z 1.5. The red colors and large inferred stellar masses in the DRGs suggest that much of the star formation in these galaxies occurred at redshifts z 5-6. Using model star-formation histories that match the DRG colors and stellar masses at z 2-3, and measurements of the UV luminosity density at z 5-6, we consider what constraints exist on the stellar initial mass function in the progenitors of the massive DRGs at z 2-3. 2005 Elsevier B.V. All rights reserved.
