Cosmic evolution of AGN with moderate-to-high radiative luminosity in the COSMOS field

TL;DR

This study analyzes the evolution of moderate-to-high luminosity AGN in the COSMOS field using deep radio survey data, deriving luminosity functions and cosmic evolution up to redshift 6, and distinguishing star formation from AGN radio emission.

Contribution

It provides the first decomposition of star formation and AGN contributions to radio emission and constrains the cosmic evolution of these AGN up to redshift 6.

Findings

Luminosity functions for HLAGN derived up to z~6.

Peak in number and luminosity density at z~1.5.

Decrease in AGN activity beyond z~1.5.

Abstract

We study the moderate-to-high radiative luminosity active galactic nuclei (HLAGN) within the VLA-COSMOS 3 GHz Large Project. The survey covers 2.6 square degrees centered on the COSMOS field with a 1$\sigma$ sensitivity of 2.3 $\mathrm{\mu Jy}$/beam across the field. This provides the simultaneously largest and deepest radio continuum survey available to date with exquisite multi-wavelength coverage. The survey yields 10,830 radio sources with signal-to-noise ratios $\geq$5. A subsample of 1,604 HLAGN is analyzed here. These were selected via a combination of X-ray luminosity and mid-infrared colors. We derive luminosity functions for these AGN and constrain their cosmic evolution out to a redshift of $z\sim6$, for the first time decomposing the star formation and AGN contributions to the radio continuum emission in the AGN. We study the evolution of number density and luminosity density finding a peak at $z\sim1.5$ followed by a decrease out to a redshift $z\sim6$.