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 A characteristic magnitude (M*) over the redshift range 0.3 z 1.7 and no evolution at higher redshifts. The rest-frame 2800 A 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 A luminosity density is almost a factor of 2 higher than that derived from the 1500 A 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 A luminosities. The extinction-corrected SFR is a factor of ~6.5 (~3.7) higher than the uncorrected SFR derived from 1500 A (2800 A) luminosity. We investigate the morphological composition of our sample by fitting Sersic profiles to the HST ACS galaxy images at a fixed rest-frame wavelength of 2800 A at 0.5 z 2.2. We find that the fraction of apparently bulge-dominated galaxies (Sersic 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.