NEW UPPER LIMITS ON INTERGALACTIC INFRARED RADIATION FROM HIGH-ENERGYASTROPHYSICS

Following our previously proposed technique, we have used the recent g amma-ray observations of Mrk 421 obtained by the Whipple Observatory t eam and the EGRET experiment on Compton Gamma-Ray Observatory as a pro be to place significant constraints on the intergalactic infrared ener gy density. Our 2 sigma upper limits are approximately 10(-8) W m-2 sr -1 for the 1-5 mum 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 r adiation produced by stars in normal galaxies.