Inhibition of star formation in barred spiral galaxies

The lack of star formation associated with the straight dust lanes within the bar of barred spiral galaxies suggests that star formation is strongly inhibited there. I have shown that the inhibition may be an effect of the high velocities, relative to the gas in the dust lanes, of the dense clouds whose orbits intersect the dust lanes. These clouds, which presumably undergo gravitational collapse upon entering the dust lanes of normal spiral galaxies, are the precursors of star formation. In barred galaxies, the clouds in the bar enter the dust lanes at a velocity an order of magnitude higher than those in normal spirals. The high velocity can cause a quick compression of the clouds followed by a rapid expansion which disperses the majority of the cloud. In the outer parts of the barred spiral galaxy, and at the very center, the cloud velocities are lower, and star formation is not inhibited. This creates the typical appearance of a barred spiral galaxy, with star formation at the ends of the bar, and in the center, but not along the predominant straight dust lanes which lie along the bar. I have tested the effectiveness of this technique by calculating the orbits of the dense, prestellar clouds in the expected gravitational field of NGC 5383. A cloud is presumed to be destroyed if its velocity relative to the intercloud gas exceeds an arbitrary minimum velocity and is presumed to collapse into stars if the intercloud density around it is enhanced by an arbitrary minimum amount