Chandra and Suzaku Follow-up Observations of Hard X-ray Selected AGN in the UDIS
Abstract
We carried out a 3 Megasecond Ultra-Deep INTEGRAL Survey (UDIS) to define a faint hard X-ray-selected AGN sample, unbiased by even the heaviest obscuration. The space density of AGN that are Compton-thick (NH>1024 cm-2) remains unknown even though it has been suggested they could nearly equal the space density of less obscured supermassive black holes. In the Ultra-Deep INTEGRAL Survey, one of the deepest surveys of the hard X-ray sky ever done, we detect 15 AGN some of which are detected in the hard X-rays for the first time. In order to measure the obscuration and the high-energy reflection component for these sources, we obtained follow-up observations with Chandra and Suzaku. Here we present X-ray spectra for all 15 AGN, including the inferred distribution of absorbing column densities. Measurement and modeling of the X-ray background provides at best an integral and degenerate constraint on AGN populations, which only weakly constrains the most obscured objects as they make only a minor contribution to the background. Direct detection of heavily obscured objects by surveys like UDIS is thus the only way to obtain a true census of their population.
- Publication:
-
American Astronomical Society Meeting Abstracts #215
- Pub Date:
- January 2010
- Bibcode:
- 2010AAS...21541115V