THE MOLECULAR GAS ENVIRONMENT AROUND TWO HERBIG Ae/Be STARS: RESOLVING THE OUTFLOWS OF LkHα 198 AND LkHα 225S

摘要

Observations of outflows associated with pre-main-sequence stars reveal details about morphology, binarity, and evolutionary states of young stellar objects. We present molecular line data from the Berkeley-Illinois-Maryland Association array and Five Colleges Radio Astronomical Observatory toward the regions containing the Herbig Ae/Be stars LkHα 198 and LkHα 225S. Single-dish observations of ~(12)CO J = 1 - 0, ~(13)CO J = 1 - 0, N_2H~+ J = 1 - 0, and CS J = 2 - 1 were made over a field of 4.3′ × 4.3′ for each species. ~(12)CO J = 1 - 0 data from FCRAO were combined with high-resolution BIMA array data to achieve a naturally weighted synthesized beam of 6.75″ × 5.5″ toward LkHα 198 and 5.7″ × 3.95″ toward LkHα 225S, representing resolution improvements of factors of approximately 10 and 5 over existing data. By using uniform weighting, we achieved another factor of 2 improvement. The outflow around LkHα 198 resolves into at least four outflows, none of which are centered on LkHα 198-IR, but even at our resolution we cannot exclude the possibility of an outflow associated with this source. In the LkHα 225S region we find evidence for two outflows associated with LkHα 225S itself, and a third outflow is likely driven by this source. Identification of the driving sources is still resolution limited and is also complicated by the presence of three clouds along the line of sight toward the Cygnus molecular cloud. ~(13)CO J = 1 - 0 is present in the environments of both stars along with cold, dense gas as traced by CS J = 2 - 1 and (in LkHα 225S) N_2H~+ J = 1 - 0. No 2.6 mm continuum is detected in either region in relatively shallow maps compared to existing continuum observations.