  Young galaxies are clumpy, gas-rich, and highly turbulent. Star formation
appears to occur by gravitational instabilities in galactic disks. The high
dispersion makes the clumps massive and the disks thick. The star formation
rate should be comparable to the gas accretion rate of the whole galaxy,
because star formation is usually rapid and the gas would be depleted quickly
otherwise. The empirical laws for star formation found locally hold at
redshifts around 2, although the molecular gas consumption time appears to be
smaller, and mergers appear to form stars with a slightly higher efficiency
than the majority of disk galaxies.
