The Great PV Cephei Outflow: A Case Study in Outflow‐Cloud Interaction

We present a set of detailed molecular line maps of the region associatedwith the giant Herbig-Haro flow HH 315, from the young star PV Cephei, aimed atstudying the outflow-cloud interaction. Our study clearly shows that the HH 315flow is effecting the kinematics of its surrounding medium, and has been ableto redistribute considerable amounts of the surrounding medium-density gas inits star-forming core as well at parsec-scale distances from the source. Thegiant molecular outflow HH 315 is a highly asymmetric bipolar flow with aprojected linear extent of about 2 pc. Our results indicate that the twooutflow lobes are each interacting with the ambient medium in different ways.The southern (redshifted) lobe interacts with a dense ambient medium, veryclose to the young stellar outflow source, and its kinetic energy is comparableto both the turbulent and gravitational binding energy of its host cloud. Inaddition, we find evidence that the southern lobe is responsible for thecreation of a cavity in the 13CO emission. In contrast, the northern (mainlyblueshifted) outflow lobe extends farther from PV Ceph and interacts withambient gas much less dense than the southern lobe. There is very little 13COemission north of the outflow source, and the only prominent 13CO emission is ashell-like structure coincident with the outer edge of the northern lobe, about1.2 pc northwest of PV Ceph. It appears that the northern lobe of the HH 315outflow has been able to ``push'' aside a substantial fraction of the gas inthe area, piling it in a dense shell-like structure at its edges. In addition,we find that the northern outflow lobe is responsible for a velocity gradientin the ambient gas.