The Star Formation and Nuclear Accretion Histories of Normal Galaxies in the AGES Survey

TL;DR

This study investigates the evolution of X-ray emission in normal galaxies over redshifts 0.1 to 0.5, revealing that star formation and black hole activity follow a (1+z)^3 trend, using stacking analysis of multiwavelength data.

Contribution

It provides new insights into the X-ray evolution of normal galaxies across a significant redshift range through combined multiwavelength stacking analysis.

Findings

X-ray emission in late-type galaxies is dominated by star formation.

Early-type galaxies' X-ray emission is from hot gas and AGN.

Star formation and black hole accretion rates evolve as (1+z)^3.

Abstract

We combine IR, optical and X-ray data from the overlapping, 9.3 square degree NOAO Deep Wide-Field Survey (NDWFS), AGN and Galaxy Evolution Survey (AGES), and XBootes Survey to measure the X-ray evolution of 6146 normal galaxies as a function of absolute optical luminosity, redshift, and spectral type over the largely unexplored redshift range 0.1 < z < 0.5. Because only the closest or brightest of the galaxies are individually detected in X-rays, we use a stacking analysis to determine the mean properties of the sample. Our results suggest that X-ray emission from spectroscopically late-type galaxies is dominated by star formation, while that from early-type galaxies is dominated by a combination of hot gas and AGN emission. We find that the mean star formation and supermassive black hole accretion rate densities evolve like (1+z)^3, in agreement with the trends found for samples of bright, individually detectable starburst galaxies and AGN. Our work also corroborates the results of many previous stacking analyses of faint source populations, with improved statistics.