The Compared Number Density of High-Redshift Galaxies and Lyman \alpha Clouds

We use our catalog of photometric redshifts in the Hubble Deep Field (HDF) to estimate the Luminosity Function (LF) of galaxies up to z=2. Using the obtained LF and a relationship between luminosity and halo size, we calculate the expected density of galactic halo crossings for any arbitrary line of sight. This density is then compared with the known one of Lyman \alpha lines, showing that the observed density of galaxies is enough to account for the observed absorption lines.