How the Spirals in the Milky Way's ISM form
  We construct a model for the Milky Way where the interstellar medium (ISM) is
equipped with self-consistent dynamics. In simulations a spiral structure
emerges from this model that is almost identical with the one in the Milky
Way's ISM. Further, the Jeans instability offers an explanation for the
observed velocity dispersion of atomic hydrogen in the ISM; this instability
vanishes from our model if we choose a velocity dispersion just above the
observed one. Surprisingly, our model gets along completely without dark
matter. The 'missing mass' distributes uniformly over the baryonic components
making it possible to explain the occurring mass gap.
