The dynamics of a complex of interlocking giant shells in the Local Group dwarf galaxy IC 1613

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Abstract
Observations have been made with the Manchester echelle spectrometer on the William Herschel telescope of the region of giant interstellar shells in the Local Group dwarf galaxy IC 1613. Photon counting imagery of this complex has revealed six giant shells with diameters of 68–308 pc. Observations of the Hα line profiles with a five element multi-slit over these shells demonstrate that systematic radial expansion is occurring in all cases. Expansion velocities range from 29–51 km s−1. Where a shell surrounds an OB association there is clear evidence that its filaments are radiatively ionized. However, it is argued that supernova explosions most likely dominate stellar winds in the creation of these giant expanding shells but this cannot be certainly confirmed until spectral types of all the enclosed blue stars are obtained and non-thermal radio emission is found. This region of interlocking giant shells could be the first stage in the formation of a >1 kpc diameter supergiant shell.