Parsec-Scale Herbig-Haro Outflows from Intermediate Mass Stars

Abstract

While there are many parsec-scale Herbig-Haro (HH) outflows known to be driven by low-mass young stars, few are associated with their intermediate mass counterparts. Here we present the discovery of five such bipolar outflows. Of these, LkHalpha 198, 1548C27 IRS1, LkHalpha 233 and LkHalpha 234 were previously known to possess small-scale HH flows, while no such activity was observed before near IRAS 19395+2313. The largest of the newly discovered outflows are seen in the vicinity of LkHalpha 234 and 1548C27 IRS1, and stretch (in projection) 8pc and 7.5pc respectively. LkHalpha 233 which was previously known to power a spectroscopically detected small-scale (< 10'') jet is now seen to drive a 3pc outflow and LkHalpha 198 is shown here to power a 2pc outflow. Two HH objects in the vicinity of IRAS 19395+2313 lead us to suggest that it may also be responsible for a 5pc outflow. In total, 27 new HH objects/complexes were discovered. Examination of these parsec-scale outflows show that they have similar lengths, morphologies, and dynamical timescales as those from low-mass sources. Many appear to have blown out of the parent cloud, suggesting that their total lengths are much greater than optically observed. The degree of collimation of these outflows is similar to those from low-mass sources suggesting that the transition to more poorly-collimated outflows must occur at higher masses than the sources observed here.