The COBE Diffuse Infrared Background Experiment search for the cosmic infrared background. I. Limits and detections

The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) spacecraft was designed primarily to conduct a systematic search for an isotropic cosmic infrared background (CIB) in 10 photometric bands from 1.25 to 240 mu m. The results of that search are presented here. Conservative limits on the CIB are obtained from the minimum observed brig htness in all-sky maps at each wavelength, with the faintest limits in the DIRBE spectral range being at 3.5 mu m (vI(v) < 64 nW m(-2) sr(-1), 95% con fidence level) and at 240 mu m (vI(v) < 28 nW m(-2) sr(-1), 95% confidence level). The bright foregrounds from interplanetary dust scattering and emis sion, stars, and interstellar dust emission are the principal impediments t o the DIRBE measurements of the GIB. These foregrounds have been modeled an d removed from the sky maps. Assessment of the random and systematic uncert ainties in the residuals and tests for isotropy show that only the 140 and 240 mu m data provide candidate detections of the GIB. The residuals and th eir uncertainties provide CIB upper limits more restrictive than the dark s ky limits at wavelengths from 1.25 to 100 mu m. No plausible solar system o r Galactic source of the observed 140 and 240 mu m residuals can be identif ied, leading to the conclusion that the CIB has been detected at levels of vI(v) = 25 +/- 7 and 14 +/- 3 nW m(-2) sr(-1) at 140 and 240 mu m, respecti vely. The integrated energy from 140 to 240 mu m, 10.3 nW m(-2) sr(-1), is about twice the integrated optical light from the galaxies in the Hubble De ep Field, suggesting that star formation might have been heavily enshrouded by dust at high redshift. The detections and upper limits reported here pr ovide new constraints on models of the history of energy-releasing processe s and dust production since the decoupling of the cosmic microwave backgrou nd from matter.