NICMOS measurements of the near-infrared background

This paper addresses the nature of the near-infrared background. We investigate whether there is an excess background at 1.4 microns, what is the source of the near-infrared background and whether that background after the subtraction of all known sources contains the signature of high-redshift objects (Z > 10). Based on NICMOS observations in the Hubble Ultra Deep Field and the Northern Hubble Deep Field we find that there is no excess in the background at 1.4 microns and that the claimed excess is due to inaccurate models of the zodiacal background. We find that the near-infrared background is now spatially resolved and is dominated by galaxies in the redshift range between 0.5 and 1.5. We find no signature than can be attributed to high-redshift sources after subtraction of all known sources either in the residual background or in the fluctuations of the residual background. We show that the color of the fluctuations from both NICMOS and Spitzer observations are consistent with low-redshift objects and inconsistent with objects at redshifts greater than 10. It is most likely that the residual fluctuation power after source subtraction is due to the outer regions of low-redshift galaxies that are below the source detection limit and therefore not removed during the source subtraction.