The X-ray background and the evolution of AGN

Citation
F. Pompilio et al., The X-ray background and the evolution of AGN, ASTRON ASTR, 353(2), 2000, pp. 440-446
Citations number
45
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
00046361 → ACNP
Volume
353
Issue
2
Year of publication
2000
Pages
440 - 446
Database
ISI
SICI code
0004-6361(200001)353:2<440:TXBATE>2.0.ZU;2-C
Abstract
We discuss the constraints on the AGN evolution from the cosmic X-ray backg round and source counts. A synthesis model to fit the X-ray background is p resented. The data used are a compilation from Gruber (1992), mainly based on HEAO-1 data. The spectrum of type 2 AGN has been modeled including Compt on down-scattering within the absorbing material. We found an improvement w hen a dependence on redshift of the relative number of obscured sources is introduced. In particular, we found a decrease of the fraction of type 2 AG N at redshifts larger than similar to 2. However, only the soft X-ray counts are well reproduced, while the hard (5- 10 keV) BeppoSAX/HELLAS source counts are underestimated by a factor of sim ilar to 1.5. A satisfactory global solution, including the good reproductio n of the hard counts, is instead obtained if the XRB normalization, recentl y obtained from BeppoSAX/MECS measurements (about 30% higher than HEAO-1), is adopted.