Citation:
Date Published:
May 1, 2009Abstract:
We combine IR, optical, and X-ray data from the overlapping, 9.3deg2 NOAO Deep Wide-Field Survey, AGN and Galaxy EvolutionSurvey (AGES), and XBoötes Survey to measure the X-ray evolution of6146 normal galaxies as a function of absolute optical luminosity,redshift, and spectral type over the largely unexplored redshift range0.1 lsim z lsim 0.5. Because only the closest or brightest of thegalaxies are individually detected in X-rays, we use a stacking analysisto determine the mean properties of the sample. Our results suggest thatX-ray emission from spectroscopically late-type galaxies is dominated bystar formation, while that from early-type galaxies is dominated by acombination of hot gas and active galactic nucleus (AGN) emission. Wefind that the mean star formation and supermassive black hole accretionrate densities evolve like ~(1 + z)3±1, in agreementwith the trends found for samples of bright, individually detectablestarburst galaxies and AGN. Our work also corroborates the results ofmany previous stacking analyses of faint source populations, withimproved statistics.