Primordial angular momentum distribution in disk galaxies and bulge to disk ratios

Motivated by the shortcomings of the CDM model in terms of galactic structure we explore a scenario in which the bulk of a disk galaxy is in place at high z. We consider the initial angular momentum distribution of this disk, finding that a tidal encounter with another galaxy can account for its present day distribution. Introducing a kinematical definition for the bulge to disk allows to calculate the disk to bulge ratio (B/D) of modeled galaxies. A comparison with a recent survey of luminosity profile decompositions shows 35% of the systems following our prediction for B/D fraction vs, disk scale length (R-d) Galaxies not following the predictions show larger B/D ratios. This is interpreted as the signature of mergers and other types of galactic interactions, which are shown to represent an important ingredient in shaping galactic populations. However, the large fraction of galaxies which do follow the model shows that many disk galaxies were fully assembled at high redshift.