Radiation-driven implosion in the Cepheus B molecular cloud

Abstract

We analyze large scale mapping observations of the molecular lines in the 12CO (J = 2 – 1), 12CO (J = 3 – 2), 13CO (J = 2 – 1), and 13CO (J = 3 – 2) transition emissions toward the Cepheus B molecular cloud with the KOSMA 3m-telescope. The integrated intensity map of the 12CO (J = 2 – 1) transition has shown a structure with a compact core and a compact ridge extended to the north-west of the core. The cloud is surrounded by an optically bright rim, where the radiation-driven implosion (RDI) may greatly change the gas properties. The intensities of the CO (J = 3 – 2) transition are higher than those of the CO (J = 2 – 1) transition along the rim area. We find characteristic RDI structure in position-velocity diagrams. Non-LTE large velocity gradient (LVG) model analysis shows that the density and temperature at the edge are higher than that in the center. Our results provide evidences that an RDI is taking place in the Cepheus B molecular cloud.