A BIPOLAR OUTFLOW FROM THE MASSIVE PROTOSTELLAR CORE W51e2-E

We present high-resolution images of the bipolar outflow from W51e2, which are produced from the Submillimeter Array archival data observed for CO(3–2) and HCN(4–3) lines with angular resolutions of 0 8 × 0 6 and 0 3 × 0 2, respectively. The images show that the powerful outflow originates from the protostellar core W51e2-E rather than from the ultracompact H ii region W51e2-W. The kinematic timescale of the outflow from W51e2-E is about 1000 yr, younger than the age (∼5000 yr) of the ultracompact H ii region W51e2-W. A large mass-loss rate of ∼1 × 10 −3 M ☉ yr −1 and a high mechanical power of 120 L ☉ are inferred, suggesting that an O star or a cluster of B stars are forming in W51e2-E. The observed outflow activity along with the inferred large accretion rate indicates that at present W51e2-E is in a rapid phase of star formation.