The Optical Extragalactic Background Light from Resolved Galaxies

We discuss the ultraviolet to near-IR galaxy counts from the deepest imaging surveys, including the northern and southern Hubble Deep Fields. The logarithmic slope of the galaxy number-magnitude relation is flatter than 0.4 in all seven UBVIJHK optical passbands at faint magnitudes, i.e. the light from resolved galaxies has converged from the UV to the near-IR. Most of the galaxy contribution to the extragalactic background light (BEL) comes from relatively bright, low-redshift objects (50% at VAB ≲ 21 and 90% at VAB ≲ 25.5). We find a lower limit to the surface brightness of the optical EBL of about 15 nW m−2 sr−1, comparable to the intensity of the far-IR background from COBE data. Diffuse light, lost because of surface brightness selection effects, may add substantially to the EBL.