Open AccessConnecting the cosmic infrared background to the X‐ray background
Author(s) -
Silva L.,
Maiolino R.,
Granato G. L.
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.1365-2966.2004.08380.x
Subject(s) - physics , cosmic infrared background , astrophysics , infrared , galaxy , luminous infrared galaxy , luminosity , x ray background , active galactic nucleus , astronomy , luminosity function , cosmic cancer database , cosmic microwave background , optics , anisotropy
We estimate the contribution of active galactic nuclei (AGN) and of their host galaxies to the infrared background. We use the luminosity function and evolution of AGN recently determined by the hard X‐ray surveys, and new spectral energy distributions connecting the X‐ray and the infrared emission, divided in intervals of absorption. These two ingredients allow us to determine the contribution of AGN to the infrared background by using mostly observed quantities, with only minor assumptions. We find that AGN emission contributes little to the infrared background (<5 per cent over most of the infrared bands), implying that the latter is dominated by star formation. However, AGN host galaxies may contribute significantly to the infrared background, and more specifically 10–20 per cent in the 1–20 μm range and ∼5 per cent at λ < 60 μm . We also give the contribution of AGN and of their host galaxies to the source number counts in various infrared bands, focusing on those which will be observed with Spitzer. We also report a significant discrepancy between the expected contribution of AGN hosts to the submillimetre background and bright submillimetre number counts with the observational constraints. We discuss the causes and implications of this discrepancy and the possible effects on the Spitzer far‐infrared bands.