Heavily Obscured AGN in the XMM-COSMOS survey
Abstract
Heavily obscured, possibly Compton Thick (CT) AGN are thought to represent an important, early phase in the AGN/Galaxy co-evolution. However, clearly identify CT beyond the local Universe is a challenging task even for the deepest X-ray surveys, while, given their low number density, large area surveys are needed to collect sizable samples. Through direct X-ray spectral analysis, pushed to the very low counts regime, we selected a small sample (∼45 sources out of 1800) of heavily obscured AGN (Log(NH)>23.5 cm^{-2}) at bright fluxes (F(2-10keV) >1×10^{-14} erg s^{-1} cm^{-2}) in the XMM-COSMOS catalog. A dozen of them are CT candidates. Trough deeper Chandra data in the same field, we tested "a posteriori" hour selection method, confirming the CT nature of 10 sources. We analyzed the distribution of BH masses and Eddington Ratios, finding significant differences between CT and non obscured sources, with the former having smaller masses and larger accretion rates, as expected in evolutionary scenarios. We also compared our results with predictions from the latest X-ray background synthesis models, finding very good agreement between the two.
- Publication:
-
The X-ray Universe 2014
- Pub Date:
- July 2014
- Bibcode:
- 2014xru..confE.270L