Type 2 AGN host galaxies in the Chandra-COSMOS Legacy Survey: No evidence of AGN-driven Quenching

Abstract

We investigate the star formation properties of a large sample of similar to 2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z similar to 3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9 < logM(stellar)/M-circle dot < 12 with uncertainties of similar to 0.19 dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M-stellar and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z > 3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs.