Evolution of the Luminosity Function, Star Formation Rate, Morphology, and Size of Star‐forming Galaxies Selected at Rest‐Frame 1500 and 2800 A

Abstract

Using the multiwavelength photometric and spectroscopic data covering the Chandra Deep Field South obtained within the Great Observatories Origins Deep Survey, we investigate the rest-frame UV properties of galaxies to z ∼ 2.2, including the evolution of the luminosity function, the luminosity density, star formation rate (SFR), and galaxy morphology. We find a significant brightening (∼1 mag) in the rest-frame 2800 Å characteristic magnitude (M*) over the redshift range 0.3 ≲ z ≲ 1.7 and no evolution at higher redshifts. The rest-frame 2800 Å luminosity density shows an increase by a factor of ∼4 over the redshift range investigated. We estimate the SFR density to z ∼ 2.2 from the 1500 and 2800 A∼ luminosities. When no correction for extinction is made, we find that the SFR derived from the 2800 Å luminosity density is almost a factor of 2 higher than that derived from the 1500 Å luminosities. Attributing this difference to differential dust extinction, we find that E(B-V) = 0.20 results in the same extinction-corrected SFR from both 1500 and 2800 Å luminosities. The extinction-corrected SFR is a factor of ∼6.5 (∼3.7) higher than the uncorrected SFR derived from 1500 Å (2800 Å) luminosity. We investigate the morphological composition of our sample by fitting Sérsic profiles to the HSTACS galaxy images at a fixed rest-frame wavelength of 2800 Å at 0.5 ≲ z ≲ 2.2. We find that the fraction of apparently bulge-dominated galaxies (Sérsic index n > 2.5) increases from ∼10% at z ∼0.5 to ∼30% at z ∼ 2.2. At the same time, we note that galaxies get bluer at increasing redshift. This suggests a scenario where an increased fraction of the star formation takes place in bulge-dominated systems at high redshift. This could be evidence that the present-day elliptical galaxies are a result of assembly (i.e., mergers) of galaxies at z ≳ 1. Finally, we find that galaxy size for a luminosity-selected sample evolves as rh ∝ (1+z)-1.1 between redshifts z = 2.2 and 1.1. This is consistent with previous measurements and suggests a similar evolution over the redshift range 0 ≲ z ≲ 6. © 2007. The American Astronomical Society. All rights reserved.