Tracing the cosmic growth of supermassive black holes to z~3 with Herschel

We study a sample of Herschel selected galaxies within the Great Observatories Origins Deep Survey-South and the Cosmic Evolution Survey fields in the framework of the Photodetector Array Camera and Spectrometer (PACS) Evolutionary Probe project. Starting from the rich multiwavelength photometric data sets available in both fields, we perform a broad-band spectral energy distribution decomposition to disentangle the possible active galactic nucleus (AGN) contribution from that related to the host galaxy. We find that 37 per cent of the Herschel-selected sample shows signatures of nuclear activity at the 99 per cent confidence level. The probability of revealing AGN activity increases for bright (L1-1000 > 10(11) L-circle dot) star-forming galaxies at z > 0.3, becoming about 80 per cent for the brightest (L1-1000 > 10(12) L-circle dot) infrared (IR) galaxies at z >= 1. Finally, we reconstruct the AGN bolometric luminosity function and the supermassive black hole growth rate across cosmic time up to z similar to 3 from a far-IR perspective. This work shows general agreement with most of the panchromatic estimates from the literature, with the global black hole growth peaking at z similar to 2 and reproducing the observed local black hole mass density with consistent values of the radiative efficiency epsilon(rad) (similar to 0.07).