ASYMMETRIES IN DISK GALAXIES - HOW OFTEN - HOW STRONG

Asymmetries in the distributions of light and neutral hydrogen are oft en observed in disk galaxies. But how common are they? Is it possible to estimate their number? Lopsided HI distributions and kinematics usu ally result in an asymmetry of the global HI profile. We have used the frequency of asymmetries in the 21 cm line profiles from several sing le-dish surveys to derive a lower limit of 50% for the fraction of gal axies with non-circularities. Asymmetries in disk galaxies may, theref ore, be the rule rather than the exception.