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

Abstract

NICMOS observations of the resolved object fluxes in the Hubble Deep Field-North and the Hubble Ultra Deep Field are significantly below the fluxes attributed to a 1.4-1.8 μm near-infrared background excess (NIRBE) from previous low spatial resolution NIRS measurements. Tests placing sources in the NICMOS image with fluxes sufficient to account for the NIRBE indicate that the NIRBE flux must be either flat on scales greater than 100'' or clumped on scales of several arcminutes to avoid detection in the NICMOS image. A fluctuation analysis of the new NICMOS data shows a fluctuation spectrum consistent with that found at the same wavelength in deep 2MASS calibration images. The fluctuation analysis shows that the majority of the fluctuation power comes from resolved galaxies at redshifts of 1.5 and less and that the fluctuations observed in the earlier deep 2MASS observations can be completely accounted for with normal low-redshift galaxies. Neither the NICMOS direct flux measurements nor the fluctuation analysis require an additional component of near-infrared flux other than the flux from normal resolved galaxies in the redshift range between 0 and 7. The residual fluctuations in the angular range between 1'' and 10'' is 1-2 nW m-2 sr-1, which is at or above several predictions of fluctuations from high redshift Population III objects, but inconsistent with attributing the entire NIRBE to high-redshift galaxies.