Models for the inner regions of the Galaxy. I

A new model is proposed for the inner regions of the Galaxy. This model involves gas flowing along concentric elliptical streamlines such as might be caused by a barlike perturbation in the gravitation field of the inner regions of the Galaxy. It is found that such a model can produce not only the so-called 3 kpc arm and the 135 km per sec arm features, but other high-velocity features as well. This model does not require a highly energetic explosion at the galactic nucleus as does the usual expanding spiral-arm model, because there is no net flow of matter out of the inner regions. This model suggests that the outer spiral-arm density wave might be associated with a barlike density wave in the inner regions of the Galaxy.