Spiral structure of the Milky Way galaxy: observations and theoretical
  predictions
  Using observational data on the kinematical properties and density
distributions of the subsystems of the Milky Way galaxy, we construct a set of
multi-component equilibrium models of its disk. The dynamics of the disk is
studied numerically using collisionless-gaseous numerical simulations. After
approximately one Gyr, a prominent central bar is formed with a semi-axis of
about three kiloparsecs. Outside the central regions, a multi-armed spiral
pattern develops, which can be characterized by the superposition of m=2, 3 and
4-armed spiral patterns. The spiral structure and the bar exist for at least 3
Gyr in our simulations. The presence of the bar in the disk of the MilkyWay
galaxy imposes rather strict limitations on the density distributions in the
subsystems of the MilkyWay galaxy.We find that bar does not form if the radial
scale length of the surface density distribution of the disk is more than 2.6
kpc. Analogously, the formation of bar is suppressed in the Milky Way disk in
models with a massive and compact stellar bulge. If future GAIA observations
confirm the existence of the three-four armed spiral pattern in the disk of the
MilkyWay, this will prove the long-term existence of spiral patterns in
galactic disks.
