FIRST RESULTS FROM A 1.3 cm EXPANDED VERY LARGE ARRAY SURVEY OF MASSIVE PROTOSTELLAR OBJECTS: G35.03+0.35

摘要

We have performed a 1.3 cm survey of 24 massive young stellar objects (MYSOs) using the Expanded Very Large Array. The sources in the sample exhibit a broad range of massive star formation signposts including infrared dark clouds (IRDCs), ultra-compact Hii (UC Hii) regions, and extended 4.5μm emission in the form of extended green objects (EGOs). In this work, we present results for G35.03+0.35 which exhibits all of these phenomena.We simultaneously image the 1.3 cm NH3 (1,1) through (6,6) inversion lines, four CH3OH transitions, two H recombination lines, plus continuum at 0.05 pc resolution.We find three areas of thermal NH3 emission, two within the EGO (designated as the NE and SW cores) and one toward an adjacent IRDC. The NE core contains a UC Hii region (CM1) and a candidate hyper-compact Hii region (CM2). A region of non-thermal, likely masing NH3 (3,3)and (6,6) emission is coincident with an arc of 44 GHz CH3OH masers. We also detect two new 25 GHz Class-I CH3OH masers. A complementary Submillimeter Array 1.3 mm continuum image shows that the distribution of dust emission is similar to the lower-lying NH3 lines, all peaking to the NWof CM2, indicating the likely presence of an additional MYSO in this protocluster. By modeling the NH3 and 1.3 mm continuum data, we obtain gas temperatures of 20–220 K and masses of 20–130 M. The diversity of continuum emission properties and gas temperatures suggests that objects in a range of evolutionary states exist concurrently in this protocluster.