The Large-Scale Structure, Kinematics, and Evolution of IC 1396

We have mapped the diffuse H II region IC 1396 in the J = 1-0 transition of CO and ¹³CO, using the FCRAO 14 m telescope with the QUARRY focal plane array receiver. The prominent bright rimmed globules are found to lie on a ring of radius 12 pc, expanding with a velocity of 5 km s^-1. The CO map extends well beyond this ring, but CO emission is found to be very weak outside the ring. The dynamical age of the system of globules, as suggested by its expansion, is 2 ∼ 3 Myr, consistent with the age estimates of the exciting O6 star, HD 206267. Nyquist-sampled CO and ¹³CO maps of selected globules show evidence of interaction with the UV radiation from HD 206267. Twenty4our IRAS point sources in the mapped field satisfy criteria of young stellar objects; 10 of these sources are directly associated with IC 1396 globules, suggesting that star formation is occurring within them. In a mass-UV flux parameter space, globules with the IRAS sources are distinct from the globules without IRAS sources, being relatively more massive. The ring of globules itself appears to be embedded in a larger elliptical structure approximately 9° (120 pc) in size, which appears in the IRAS maps of 60 and 100 microns emission. We suggest that star formation in the Cepheus region has proceeded by sequential triggering, and the stars forming in the globules of IC 1396 represent the youngest generation of stars in this region.