CO Multi-line Observations of HH 80–81: A Two-component Molecular Outflow Associated with the Largest Protostellar Jet in Our Galaxy

Abstract

Stretching a length reaching 10 pc projected in the plane of sky, the radio jet associated with Herbig-Haro objects 80 and 81 (HH 80-81) is known as the largest and best collimated protostellar jet in our Galaxy. The nature of the molecular outflow associated with this extraordinary jet remains an unsolved question which is of great interests to our understanding of the relationship between jets and outflows in high-mass star formation. Here we present Atacama Pathfinder EXperiment CO (6-5) and (7-6), James Clerk Maxwell Telescope CO (3-2), Caltech Submillimeter Observatory CO (2-1), and Submillimeter Array CO and 13 CO (2-1) mapping observations of the outflow. We report on the detection of a two-component outflow consisting of a collimated component along the jet path and a wide-angle component with an opening angle of about 30 • . The gas velocity structure suggests that each of the two components traces part of a primary wind. From LVG calculations of the CO lines, the outflowing gas has a temperature around 88 K, indicating that the gas is being heated by shocks. Based on the CO (6-5) data, the outflow mass is estimated to be a few M ⊙ , which is dominated by the wide-angle component. A comparison between the HH 80-81 outflow and other well shaped massive outflows suggests that the opening angle of massive outflows continues to increase over time. Therefore, the mass loss process in the formation of early-B stars seems to be similar to that in low-mass star formation, except that a jet component would disappear as the central source evolves to an ultracompact HII region.

Modeling the Accretion Disk around the High-mass Protostar GGD 27-MM1

“…They obtain a mass-loss rate of Ṁout ∼10 −5 M yr −1 for a distance of 1.7 kpc, 8×10 −6 M yr −1 for the corrected distance of 1.4 kpc (see appendix). This value is in agreement with the value obtained from CO observations of the molecular outflow associated with the jet (Qiu et al 2019). Assuming the accretion rate Ṁacc of the disk onto the star to be ∼10 times larger than the mass-loss rate (Bontemps et al 1996), the mass accretion rate would be Ṁacc ∼ 8×10 −5 M yr −1 .…”

A Highly Collimated Flow from the High-mass Protostar ISOSS J23053+5953 SMM2

“…This number seems reasonable despite the relatively low temperature of most of the core gas, as some shock heating in the outflow is expected. Similar numbers are also suggested by multi-line studies (e.g., Qiu et al 2019), and in the most extreme cases values up to 1000 K have been reported (Su et al 2012). For our case, if the assumed excitation temperature is larger than the assumed 50 K that would lead to substantially larger outflow mass, and thereby result in increased values for the energetic flow parameters.…”

Multiline Observations of Molecular Bullets from a High-mass Protostar

“…Therefore there is no further presentation or discussion on the CO 7-6 line in this work. The data presented here come from the same observing program as those presented in Qiu et al (2019). Readers are referred to Qiu et al (2019) for a detailed description of the observations and relevant parameters.…”

“…reported the first detection of molecular bullets in high-mass star-forming region HH 80-81, which has a bolometric luminosity of 2×10 4 L ⊙ at an adopted distance of 1.7 kpc (Rodriguez et al 1980). This region is best known for a spectacular (10.3 pc long) radio jet, which is launched from a high-mass star-forming core, namely MM1, and powered by an early B-type protostar (Martí et al 1993(Martí et al , 1995(Martí et al , 1998Masqué et al 2012Masqué et al , 2015Qiu et al 2019). Another molecular cloud core, MM2, with a mass > 12 M ⊙ , is separated by about 7 ′′ from MM1 and appears to be at an earlier evolutionary stage Fernández-López et al 2011).…”