The inhibition of star formation in barred spiral galaxies

It is shown that the inhibition of star formation suggested by observations of the straight dust lanes within the bar of barred spiral galaxies may be a consequence of the high velocities, relative to the gas in the dust lanes, of the dense clouds whose orbits intersect the dust lanes. In barred galaxies, the clouds in the bar enter the dust lanes at a velocity that is an order of magnitude higher than those in normal spirals and can lead to a quick compression of the clouds followed by a rapid expansion which disperses most of the cloud. Because at the outer parts of such a galaxy and at the center cloud velocities are lower, star formation is not inhibited and the typical appearance of barred spiral galaxies results. The effectiveness of this mechanism is tested by calculating the orbits of the dense, prestellar clouds in the expected gravitational field of NGC 5383.