A correlation between star formation rate and average black hole accretion in star-forming galaxies

Abstract

We present a measurement of the average supermassive black hole accretion rate (BHAR) as a function of the star formation rate (SFR) for galaxies in the redshift range 0.25 < z < 0.8. We study a sample of 1767 far-IR-selected star-forming galaxies in the 9 deg2 Boötes multi-wavelength survey field. The SFR is estimated using 250 μm observations from the Herschel Space Observatory, for which the contribution from the active galactic nucleus (AGN) is minimal. In this sample, 121 AGNs are directly identified using X-ray or mid-IR selection criteria. We combined these detected AGNs and an X-ray stacking analysis for undetected sources to study the average BHAR for all of the star-forming galaxies in our sample. We find an almost linear relation between the average BHAR (in M⊙ yr-1) and the SFR (in M⊙ yr-1) for galaxies across a wide SFR range 0.85 < log SFR < 2.56: log BHAR = (- 3.72 ± 0.52) + (1.05 ± 0.33)log SFR. This global correlation between SFR and average BHAR is consistent with a simple picture in which SFR and AGN activity are tightly linked over galaxy evolution timescales. © 2013. The American Astronomical Society. All rights reserved.