The Episodic, Precessing Giant Molecular Outflow from IRAS 04239+2436 (HH 300)

We present the first set of detailed molecular line maps of the regionassociated with the giant Herbig-Haro flow HH 300, from the young star IRAS04239+2436. Our results indicate that the red lobe of the HH 300 flow isdepositing a fair amount of momentum and kinetic energy over a notable volumeof its host dark cloud. This makes HH 300 a key player in the evolution andfate of its parent cloud. The redshifted molecular outflow lobe of HH 300 is1.1 pc long and 0.3 pc wide, and has a very clumpy structure. The density,velocity, and momentum distributions in the outflow indicate that the observedclumps arise from the prompt entrainment of ambient gas. Bow shock-shapedstructures are associated with the clumps, and we hypothesize that the shocksare produced by different mass ejection episodes. Lines drawn from IRAS04239+2436 to each of these clumps have different orientations on the plane ofthe sky, and we conclude that HH 300 is a precessing and episodic outflow. Theobservations include a map of the red lobe in the 12CO(2-1) line, with a beamsize of 27'', and more extended maps of the outflow region in the 12CO(1-0) and13CO(1-0) lines, with 45'' and 47'' beam sizes, respectively. We obtain a steeppower-law mass spectrum for HH 300, which we believe is best explained by theevolution of the outflow mass kinematics. In addition, our 13CO observationsshow that the HH 300 flow has been able to redistribute (in space and velocity)considerable amounts of its surrounding medium-density gas.