A HIGH-SPATIAL-RESOLUTION STUDY OF THE ON2 MASSIVE STAR-FORMING REGION

We present 5 ''-10 '' resolution images of the ON2 cloud core in the m olecular lines (CO)-C-12(J = 1-0), SiO(v = 0, J = 2-1), (HCO+)-C-13(J = 1-0), and SO2(8(3.5)-9(2.8)) and 3 millimeter continuum obtained wit h the Berkeley-Illinois-Maryland Array (BIMA) millimeter-wave interfer ometer. For the (CO)-C-12 line, additional observations were obtained with the NRAO(4) 12 m telescope to recover extended emission missed by the interferometer. We find evidence for at least four massive, energ etic molecular outflows from young stellar objects within a 1.5 pc reg ion. Three of these are identified by bipolar high-velocity (CO)-C-12 emission, and a fourth is suggested by SiO and SO2 emission. Continuum emission is detected from the ultracompact (UC) H II region, G75.78 0.34, and also from two deeply embedded YSOs, one of which (source 3) may be the driving engine of the dominant central outflow G75 C. Appr oximately half of the SiO emission observed is not obviously linked to the proposed molecular outflows and perhaps traces additional shock a ctivity within ON2. The high-resolution observations support the concl usion reached previously that a near-simultaneous massive star formati on event occurred in the ON2 complex similar to 10(4) yr ago. The pres ence of molecular outflows in the cloud core shows that this event was not isolated to the cloud edges.