A galaxy is a large gravitational aggregation of stars, dust, gas, and an unknown component termed dark matter.
Beyond the nuclear bulge lies a large disc containing young, hot stars, called the disk of the galaxy.
The primordial vorticity theory predicts that the spin vectors of galaxies are distributed primarily perpendicular to the cluster plane.
In the turbulence scenario, first flattened rotating proto-clusters formed due to cosmic vorticity in the early universe.
According to the primordial vorticity theory, the presence of large chaotic velocities generates turbulence, which, in turn, produces density and pressure fluctuations.
Galaxies form when unbound galactic mass eddies, expanding faster than their bound cluster background.
According to the non-linear gravitational instability theory, a growth of small inhomogeneities leads to the formation of thin, dense, and gaseous condensations that are called `pancakes'.
These condensations are compressed and heated to high temperatures by shock waves causing them to quickly fragment into gas clouds.
In this scheme, one could imagine that large irregularities like galaxies grew under the influence of gravities from small imperfections in the early universe.
The angular momentum transferred to a developing proto-galaxy by the gravitational interaction of the quadrupole moment of the system with the tidal field of the matter.