Bow Shocks, Wiggling Jets, and Wide‐Angle Winds: A High‐Resolution Study of the Entrainment Mechanism of the PV Cephei Molecular (CO) Outflow

We present a new set of high-resolution molecular line maps of the gasimmediately surrounding various Herbig-Haro (HH) knots of the giant HH flow HH315, from the young star PV Cephei. The observations, aimed at studying theentrainment mechanism of the 2.6 pc-long HH 315 flow, include IRAM 30m maps ofthe 12CO(2-1), 12CO(1-0), and 13CO(1-0) lines, with beam sizes of 11'', 21'',and 22'', respectively. We compare the morphology and the kinematics of theoutflow gas, as well as the temperature and momentum distribution of themolecular outflow with those predicted by different entrainment models. Withour detailed study we are able to conclude that jet bow shock entrainment by anepisodic stellar wind, with a time-varying axis, produces most of thehigh-velocity molecular outflow observed far from the source. In addition, nearPV Cephei we find evidence for a poorly collimated, wide-angle, molecularoutflow and a collimated wiggling jet-like molecular outflow. We propose thatthe poorly collimated component is entrained by a wide-angle wind, and thecollimated component is entrained by a variable jet with internal workingsurfaces. If this picture is true, then a stellar wind model which allows forthe coexistence of a wide-angle component and a collimated (jet-like) stellarwind component is needed to explain the observed properties of the PV Cephoutflow. The wiggling axis of the redshifted molecular outflow lobe indicatesthat the outflow ejection axis is changing over time. We find that thetime-scale of the axis variation shown by the molecular outflow lobe is about afactor of 10 less than that shown by the large-scale optical HH knots.