  We used fully cosmological, high resolution N-body + SPH simulations to
follow the formation of disk galaxies with a rotational velocity between 140
and 280 Km/sec in a Lambda CDM universe. The simulations include gas cooling,
star formation, the effects of a uniform UV background and a physically
motivated description of feedback from supernovae. The host dark matter halos
have a spin and last major merger redshift typical of galaxy sized halos as
measured in recent large scale N-Body simulations. Galaxies formed rotationally
supported disks with realistic exponential scale lengths and fall on the I-band
and baryonic Tully Fisher relations. The combination of UV background and SN
feedback drastically reduced the number of visible satellites orbiting inside a
Milky Way sized halo, bringing it fair agreement with observations. Feedback
delays SF in small galaxies and more massive ones contain older stellar
populations. The current star formation rates as a function of galaxy stellar
mass are in good agreement with those measured by the SDSS.
