Extragalactic Background Light

People involved at OAB: Pozzetti.

We have analysed 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 bandpasses at faint magnitudes, i.e. the light from resolved galaxies has converged from the UV to the near-IR. We find a lower limit to the surface brightness of the optical EBL 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. Most of the galaxy contribution to the resolved extragalactic background light (EBL) comes from relatively bright (50% at $V<21$ and 90% at $V<25.5$), at relatively low-redshift ($z<1$) objects We have moreover estimated the contribution to the optical EBL from two populations of high redshift sources, the Lyman-break galaxies (LBGs) and the extremely red objects (EROs), and derived the predictions for EBL using different star formation histories (Pozzetti & Madau 2001).