Gould's Belt
  The local velocity patterns of star forming regions, young OB stars, nearby
OB associations, atomic and molecular gas are confronted with models of an
expanding region. We test free expansion from a point or from a ring, expanding
2D shell, and expanding 3D belt with abrupt or gradual energy injection
snow-plowing the ambient medium with or without the drag forces including
fragmentation and porosity of the medium. There is no agreement on the
expansion time, which varies from 30 - 100 Myr. The inclination of the Gould
belt is not explained by the above models of expansion. An oblique impact of a
high velocity cloud may explain it, but the observed velocity pattern is
difficult to reproduce. The Gould's belt may be one of the many structures
resulting from shell-shell collisions in the galactic plane. The origin of the
Gould's belt may be connected to instabilities in the curling gas flows
downstream from the Galaxy spiral arms, forming ISM clouds and star formation
complexes.
