Open AccessThe (un)resolved X‐ray background in the Lockman Hole
Author(s) -
Worsley M. A.,
Fabian A. C.,
Barcons X.,
Mateos S.,
Hasinger G.,
Brunner H.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08142.x
Subject(s) - physics , astrophysics , x ray background , active galactic nucleus , flux (metallurgy) , x ray , astronomy , galaxy , optics , materials science , metallurgy
ABSTRACT Most of the soft and a growing fraction of the harder X‐ray background has been resolved into emission from point sources, yet the resolved fraction above 7 keV has only been poorly constrained. We use ∼700 ks of XMM–Newton observations of the Lockman Hole and a photometric approach to estimate the total flux attributable to resolved sources in a number of different energy bands. We find the resolved fraction of the X‐ray background to be ∼90 per cent below 2 keV but it decreases rapidly at higher energies with the resolved fraction above ∼7 keV being only ∼50 per cent. The integrated X‐ray spectrum from detected sources has a slope of Γ∼ 1.75, much softer than the Γ= 1.4 of the total background spectrum. The unresolved background component has the spectral signature of highly obscured active galactic nuclei.