Detection in Hα of a Supershell Associated with W4

摘要

From H I observations, Normandeau, Taylor, & Dewdney have identified a possible Galactic chimney emanating from W4. We observed a 10° diameter field centered on this region in the Hα line using a CCD camera sensitive to faint extended emission. Our image shows an apparent shell of H II, which we interpret as the ionized inner wall of a superbubble produced by stellar winds from the very young star cluster OCl 352. An analysis of the ionization balance indicates that much of the Lyman continuum radiation from the star cluster is absorbed and does not escape from the disk.