New constraints on the cosmic mid-infrared background using TeV gamma-ray astronomy

Abstract

Very high energy gamma-ray data obtained by CAT and HEGRA from the active galactic nucleus Mkn 501 are used to constrain the cosmic Mid-Infrared background. While the entire infrared and submillimeter spectrum shape based on models has been fixed and the density scaled as a whole in previous studies, recent measures on the low and high energy infrared background are extensively used in this paper. In this original approach the infrared distribution is only varied in the unexplored 3.5-100 μm region. With a conservative hypothesis on the intrinsic spectrum of Mkn 501, an upper limit of 4.7 nW m-2 sr-1 between 5 and 15 μm is derived, which is very close to the lower limit inferred from deep ISOCAM cosmological surveys at 15 μm. This result is shown to be independent of the exact density of the λ < 3.5 μm and λ > 100 μm infrared distribution within the uncertainties of the measurements. Moreover, the study presented here rules out a complete extragalactic origin for the 60 micron tentative background detection as found by Finkbeiner et al. (2000).