Diffuse Extragalactic Background Light versus Deep Galaxy Counts in the Subaru Deep Field: Missing Light in the Universe?

Abstract

Deep optical and near-infrared galaxy counts are utilized to estimate the extragalactic background light (EBL) coming from normal galactic light in the universe. Although the slope of the number-magnitude relation of the faintest counts is flat enough for the count integration to converge, a considerable fraction of EBL from galaxies could still have been missed in deep galaxy surveys because of various selection effects, including the cosmological dimming of the surface brightness of galaxies. Here we give an estimate of EBL from galaxy counts, in which these selection effects are quantitatively taken into account for the first time, based on reasonable models of galaxy evolution that are consistent with all available data of galaxy counts, size, and redshift distributions. We show that the EBL from galaxies is best resolved into discrete galaxies in the near-infrared bands (J, K) by using the latest data of the Subaru Deep Field; more than 80%-90% of EBL from galaxies has been resolved in these bands. Our result indicates that the contribution by missing galaxies cannot account for the discrepancy between the count integration and recent tentative detections of diffuse EBL in the K band (2.2 μm), and there may be a very diffuse component of EBL that has left no imprints in known galaxy populations.