New Upper Limits on Intergalactic Infrared Radiation from High-Energy Astrophysics

Abstract

Following our previously proposed technique, we have used the recent γ-ray observations of Mrk 421 obtained by the Whipple Observatory team and the EGRET experiment on Compton Gamma-Ray Observatory as a probe to place significant constraints on the intergalactic infrared energy density. Our 2 a upper limits are ∼10 -8 W m -2 sr -1 for the 1-5 μm range. These constraints are much better than those obtained by direct measurements. They rule out more exotic mechanisms for producing a large intergalactic IR flux and are consistent with radiation produced by stars in normal galaxies