SIMBAD references

Asymmetries in the distributions of light and neutral hydrogen are often observed in disk galaxies. But how common are they? It is possible to estimate their number? Lopsided HI distributions and kinematics usually result in an asymmetry of the global HI profile. We have used the frequency of asymmetries in the 21 cm line profiles from several single-dish surveys to derive a lower limit of 50% for the fraction of galaxies with non-circularities. Asymmetries in disk galaxies may, therefore, be the rule rather than the exception.