A Tentative detection of the cosmic infrared background at 3.5 mu m from COBE/DIRBE observations

Foreground emission and scattered light from interplanetary dust (IPD) part icles and emission from Galactic stellar sources are the greatest obstacles to determining the cosmic infrared background (CIB) from diffuse sky measu rements in the similar to 1-5 mu m range. We use ground-based observational limits on the K-band intensity of the CIB in conjunction with sky maps obt ained by the Diffuse Infrared Background Experiment (DIRBE) on the Cosmic B ackground Explorer satellite to reexamine the limits on the CIB at 1.25, 3. 5, and 4.9 mu m. Adopting a CIB intensity of 7.4 nW m(-2) sr(-1) at 2.2 mu m, and using the 2.2 mu m DIRBE sky map from which the emission from the IP D cloud has been subtracted, we create a spatial template of the Galactic s tellar contribution to the diffUse infrared sky. This template is then used to subtract the contribution of the diffuse Galactic stellar emission from the IPD emission-subtracted DIRBE sky maps at 1.25, 3.5, and 4.9 mu m. The DIRBE 100 mu m data are used to estimate the small contribution of emissio n from interstellar dust at 3.5 and 4.9 mu m. Our method significantly redu ces the errors associated with the subtraction of Galactic starlight, leavi ng only the IPD emission component as the primary obstacle to the detection of the CIB at these wavelengths. The analysis leads to a tentative detecti on of the CIB at 3.5 mu m with an intensity of vI(v) = (9.9 +/- 0.312[v(o)I (CIB)(v(o)) - 7.4]} +/- 2.9 nW m(-2) sr(-1), where v(o)I(CIB)(v(o)) is the CIB intensity at 2.2 mu m in units of nW m(-2) sr(-1). The analysis also yi elds new upper Limits (95% confidence limit) on the CIB at 1.25 and 4.9 mu m of 68 and 36 nW m(-2) sr(-1), respectively The cosmological implications of these results are discussed in this Letter.