A PARSEC-SCALE HERBIG-HARO JET IN BARNARD-5

We report the discovery of a parsec-scale, jetlike, bipolar Herbig-Har o flow, HH 366, emerging from the young stellar object IRS 1, which is embedded in the dark cloud Barnard 5 (B5) at the eastern end of the P erseus molecular cloud complex. The jet is about 22' in extent, which corresponds to a projected length of about 2.2 pc (assuming a distance of 350 pc), and is less than 1' (0.1 pc) wide. The brighter southwest ern end of the jet is receding with a velocity between 30 and 100 km s (-1). The fainter eastern lobe is blueshifted with a slightly lower ra dial velocity amplitude. The blueshifted jet emerges from IRS I at a p osition angle of about 75 degrees. Both the redshifted and blueshifted portions of the how are brightest at their ends (the most distant poi nts from the source). In the blueshifted eastern lobe, faint emission can be traced to within several arcminutes of the source, while the re dshifted lobe emerges from behind the cloud core about 5' southwest of IRS 1. The orientation and kinematics of the Herbig-Haro jet matches that of the inner portion of the CO outflow from IRS 1 mapped at high- angular resolution by Fuller et al. A reanalysis of the Goldsmith et a l. (CO)-C-12 data shows that an envelope of high-velocity molecular ga s extends from IRS I to both the eastern and western ends of the Herbi g-Haro jet. The redshifted lobe of CO emission lying several arc-minut es north of IRS 3 (an infrared source located about 10' to the southwe st of IRS I) coincides with the southwestern (redshifted) optical lobe of the B5 jet. Although previously associated with IRS 3, this lobe i s the brightest portion of the southwestern lobe of the IRS 1 CO outfl ow. Both the CO flow and the HH jet are nearly orthogonal to a 0.06 pc long ridge or extended ''pseudodisk'' of dense molecular gas seen in tracers such as HCN. The two lobes of the IRS I optical outflow are mi saligned; the red-shifted lobe appears to be deflected south with resp ect to the axis inferred by connecting B5 IRS1 to the end of the blues hifted lobe. A roughly 5-10 km s(-1) motion of the source with respect to the host cloud could produce this misalignment. The IRS I outflow provides evidence for outflow models in which CO is entrained from den se molecular gas by a hypersonic jet. A second Herbig-Haro flow, HH 36 7, is located 1' southeast (at position angle 155 degrees) of the infr ared source B5 IRS 3.