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 molecular lines 12 CO( J = 1-0), SiO( v = 0, J = 2-1), H 13 CO + ( J = 1-0), and SO 2 (8 3,5 -9 2,8 ) and 3 millimeter continuum obtained with the Berkeley-Illinois-Maryland Array (BIMA) millimeter-wave interferometer. For the 12 CO line, additional observations were obtained with the NRAO 12 m telescope to recover extended emission missed by the interferometer. We find evidence for at least four massive, energetic molecular outflows from young stellar objects within a 1.5 pc region. Three of these are identified by bipolar high-velocity 12 CO emission, and a fourth is suggested by SiO and SO 2 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. Approximately half of the SiO emission observed is not obviously linked to the proposed molecular outflows and perhaps traces additional shock activity within ON2. The high-resolution observations support the conclusion reached previously that a near-simultaneous massive star formation event occurred in the ON2 complex ~10 4 yr ago. The presence of molecular outflows in the cloud core shows that this event was not isolated to the cloud edges.