2001ApJ...554..132A

We present the first set of detailed molecular-line maps of the region associated with the giant Herbig-Haro flow HH 300 from the young star IRAS 04239+2436. Our results indicate that the red lobe of the HH 300 flow is depositing a fair amount of momentum [3.2(sini)^–1 M_☉ km.s^–1] and kinetic energy [2.6(sini)^–2x10⁴³ ergs] over a notable volume (∼11%) of its host dark cloud. This makes HH 300 a key player in the evolution and fate of its parent cloud. The redshifted molecular outflow lobe of HH 300 is 1.1 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 observed clumps arise from the prompt entrainment of ambient gas. Bow shock-shaped structures are associated with the clumps, and we hypothesize that the shocks are produced by different mass ejection episodes. Lines drawn from IRAS 04239+2436 to each of these clumps have different orientations on the plane of the sky, and we conclude that HH 300 is a precessing and episodic outflow. The observations include a map of the red lobe in the CO(2-1) line, with a beam size of 27", and more extended maps of the outflow region in the ¹²CO(1-0) and ¹³CO(1-0) lines, with 45" and 47" beam sizes, respectively. Due to ``contamination'' by emission from another molecular cloud along the same line of sight, we are not able to study the blueshifted lobe of HH 300. The combined ¹²CO (1-0) and ¹³CO(1-0) line observations enable us to estimate the outflow mass accounting for the velocity-dependent opacity of the ¹²CO(1-0) line. This method is much more precise than using ¹²CO data alone. We obtain a steep power-law mass spectrum for HH 300, which we believe is best explained by the evolution of the outflow mass kinematics. In addition, our ¹³CO(1-0) observations show that the HH 300 flow has been able to redistribute (in space and velocity) considerable amounts of its surrounding medium-density (∼10³ cm^–3) gas.