Molecular Line Observations Of The Small Protostellar Group L1251B

We present molecular line observations of L1251B, a small group of pre- and protostellar objects, and its immediate environment in the dense (CO)-O-18 core L1251E. These data are complementary to near-infrared, submillimeter, and millimeter continuum observations reported by Lee et al. The single-dish data of L1251B described here show very complex kinematics, including infall, rotation, and outflow motions, and the interferometer data reveal these in greater detail. Interferometer data of N2H+ 1-0 suggest a very rapidly rotating flattened envelope between two young stellar objects, IRS1 and IRS2. In addition, interferometer data of CO 2-1 resolve the outflow associated with L1251B seen in single-dish maps into a few narrow and compact components. Furthermore, the high-resolution data support recent theoretical studies of molecular depletions and enhancements that accompany the formation of protostars within dense cores. Beyond L1251B, single-dish data are also presented of a dense core located similar to 150 '' to the east that Lee et al. detected at 850 mu m, but that has no associated point sources at near- and mid-infrared wavelengths. The relative brightness between molecules, which have different chemical timescales, suggests that it is less chemically evolved than L1251B. This core may be a site for future star formation, however, since line profiles of HCO+, CS, and HCN show asymmetry with a stronger blue peak, which is interpreted as an infall signature.