A high resolution hydrogen-line survey of Messier 31. III : H I holes in the interstellar medium

An analysis is carried out of H I holes in M 31 as detected with the Westerbork radiotelescope. The holes range from 100-1000 pc across and represent missing masses ranging from 1000-10 million solar masses, which would require energies ranging from 10 to the 49th to 10 to the 53rd erg. The kinematic ages are projected to be from 2.5-30 million years, with the production rate of the holes being 1/100,000 yr. The production rate estimate is used to derive a lower limit for the occurrence of supernovae in M 31, about 0.001/yr. Finally, a correlation is found between H I holes smaller than 300 pc and OB associations and H II regions.