Abstract
Several scenarios have been proposed to explain the existence of H I holes in galaxies. In this work, the properties of the holes and shells in the nearby dwarf galaxy IC 2574 are used to test the different models. We report that the distribution of the kinematic ages of the holes located at the receding side of the galaxy is remarkably different from the distribution for the holes situated at the approaching side. The mean values of the kinematic ages are 16.45+/-5.0 Myr and 30.0+/-13.0[10.5] Myr, respectively. We estimate a probability of less than 4×10-3 that the age distributions were drawn at random. An asymmetry between both sides is also found in the photometric properties and in the H I mass. These results are interpreted as evidence in favor of a connection between the star formation activity and the formation of holes in the interstellar medium, in accordance with the predictions of the classical hypothesis that shells are created by multiple supernova explosions. In addition, we find that the alternative scenarios face substantial difficulties and, so far, none of them can convincingly explain the observed abundance of spherically expanding shells. After an examination of the different alternative models, we conclude that most of the holes in IC 2574 are likely the result of multiple supernova explosions.
