Hard X-ray spectral properties of distant AGN in the NuSTAR surveys
Abstract
I will present a study on the average broad X-ray band (~0.5-30 keV) spectral properties of the NuSTAR sources detected in the ECDF-S, EGS and COSMOS fields. Constructing the rest-frame composite spectra of AGN in different hydrogen column density (NH) and 10-40 keV luminosity bins, using Chandra and NuSTAR data, we investigate the typical spectral parameters of the AGN population, such as the photon index, NH, strength of the iron emission line (~6.4 keV) and of the Compton reflection at ~20-30 keV. Placing constraints on the reflection fraction (R) is of particular importance for the synthesis models of the cosmic X-ray background (CXB), as this parameter is strongly linked with the fraction of Compton-thick AGN needed to fit the CXB spectrum. Thanks to its sensitivity at ~20-30 keV, NuSTAR allows for the first time, to directly place such constraints for non-local AGN.
We find typical reflection fractions of R~1-1.5, consistent the AGN in the local Universe, with a tentative evidence for the most obscured AGN to have, on average, stronger Compton reflection compared to unobscured AGN. Moreover, contrary to previous works, we do not find significant evidence for a decrease of the reflection strength with luminosity for typical Γ=1.8-1.9. Our results support CXB models that require a relatively small fraction of CT AGN, of the order of ~10-15%.- Publication:
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Active Galactic Nuclei: What's in a Name?
- Pub Date:
- August 2016
- DOI:
- 10.5281/zenodo.60393
- Bibcode:
- 2016agnw.confE..24D
- Keywords:
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- Active Galactic Nuclei;
- Zenodo community agn2016