Searching for Heavily Obscured AGN at High Redshift with the SAFARI-SPICA Spectro-Photometer

¹ Dipartimento di Astronomia, Bologna, Italy
² Istituto Nazionale di Astronomia, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
³ Istituto Nazionale di Astronomia, IFSI, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy

Abstract

Heavily obscured and Compton-thick Active Galactic Nuclei (AGN) may remain undetected even in the deepest X-ray and optical surveys. In the last few years, thanks to Spitzer observations, it has been realized that mid-IR (MIR) observations can provide a viable and, in some cases, unique alternative to X-ray and optical searches for the most obscured AGN. The Spitzer spectrometer IRS has identified some of these sources up to z ~ 2.5 (due to the spectral coverage), and, by characterizing the MIR spectrum, has allowed to disentangle the different contribution of accretion and star-formation processes to the observed MIR emission. The spectro-photometry mode of SAFARI, on board of SPICA, will extend the IRS study to higher redshift (> 2.5 − 3), characterizing the restframe MIR spectrum of dust-obscured galaxies and AGNs. This will allow us to witness the dust-enshrouded blackhole/galaxy formation epoch.