Scientific Seminars

Chasing up obscured AGN with the Swift-INTEGRAL X-ray (SIX) survey

E. Bottacini

2011-12-19    11.30    Merate - POE

The Cosmic X-ray Background (CXB) is produced by accretion of gas onto the super-massive black holes (SMBHs) harbored at the center of Active Galactic Nuclei (AGN). The shape of the CXB predicts that most of the accretion occurs in environments that are heavily obscured by dust and gas. Despite this prediction, the currently flying and most sensitive hard X-ray missions Swift and INTEGRAL are detecting fewer obscured AGN than expected. Therefore roughly 99% of the CXB is so far unresolved at hard X-ray energies. I address the open question of the missing detection of obscured AGN with the combined Swift and INTEGRAL hard X-ray (SIX) survey. This survey is obtained by combining the Swift/BAT and INTEGRAL/ISGRI observations with resampling and merging techniques. As a result the SIX survey is a factor ~4 more sensitive than the surveys of BAT and ISGRI alone. Our sample comprises ~100 AGN and a number of unidentified sources. I determine the contribution of our identified source sample to the CXB. The scientific outcome of the sample has been properly addressed to study the evolution of the AGN at redshift below 0.4. Our sample of faint sources are suitable targets for the new generation X-ray telescopes with focusing techniques such as NuSTAR that will be launched in 2012.