Constraints on the Cosmic Near‐Infrared Background Excess from NICMOS Deep Field Observations

NICMOS observations of the resolved object fluxes in the Hubble Deep FieldNorth and the Hubble Ultra Deep Field are significantly below the fluxesattributed to a 1.4 - 1.8 microns Near InfraRed Background Excess (NIRBE) fromprevious low spatial resolution NIRS measurements. Tests placing sources in theNICMOS image with fluxes sufficient to account for the NIRBE indicate that theNIRBE flux must be either flat on scales greater than 100 arc second or clumpedon scales of several arc minutes to avoid detection in the NICMOS image. Afluctuation analysis of the new NICMOS data shows a fluctuation spectrumconsistent with that found at the same wavelength in deep 2MASS calibrationimages. The fluctuation analysis shows that the majority of the fluctuationpower comes from resolved galaxies at redshifts of 1.5 and less and that thefluctuations observed in the earlier deep 2MASS observations can be completelyaccounted for with normal low redshift galaxies. Neither the NICMOS direct fluxmeasurements nor the fluctuation analysis require an additional component ofnear infrared flux other than the flux from normal resolved galaxies in theredshift range between 0 and 7. The residual fluctuations in the angular rangebetween 1 and 10 arc seconds is 1-2 nW m-2 sr-1 which is at or above severalpredictions of fluctuations from high redshift population III objects, butinconsistent with attributing the entire NIRBE to high redshift galaxies.Comment: Accepted for publication in the Astrophysical Journa