Abstract
Context. Measurements of the Extragalactic Background Light (EBL) are a
fundamental source of information on the collective emission of cosmic sources.
Aims. At infrared wavelengths, however, these measurements are precluded by
the overwhelming dominance from Interplanetary Dust emission and the Galactic
infrared foreground. Only at $> 300 \ \mu$m, where the foregrounds are
minimal, has the Infrared EBL (IR EBL) been inferred from analysis of the COBE
maps. The present paper aims to assess the possibility of evaluating the IR EBL
from a few $\mu$m up to the peak of the emission at >100 $\mu$m using an
indirect method that avoids the foreground problem.
Methods. To this purpose we exploit the effect of pair-production from
gamma-gamma interaction by considering the highest energy photons emitted by
extragalactic sources and their interaction with the IR EBL photons. We
simulate observations of a variety of low redshift emitters with the
forthcoming Imaging Atmospheric Cherenkov Telescope (IACT) arrays (CTA in
particular) and water Cherenkov observatories (LHAASO, HAWC, SWGO) to assess
their suitability to constrain the EBL at such long wavelengths.
Results. We find that, even under the most extremely favorable conditions of
huge emission flares, extremely high-energy emitting blazars are not very
useful for our purpose because they are much too distant (>100 Mpc the nearest
ones, MKN 501 and MKN 421). Observations of more local Very High Energy (VHE)
emitting AGNs, like low-redshift radio galaxies (M87, IC 310, Centaurus A), are
better suited and will potentially allow us to constrain the EBL up to $łambda
100\ \mu$m.
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