2007A&A...461..197W

The high angular resolution images with the Very Large Array (VLA) allow us to explore the general properties of protostellar cores in massive star forming regions at large distances. We observed the NH₃(J,K)=(1,1) and (2,2) lines toward five massive protostar candidates (IRAS 18196-1331, IRAS 18352-0148, IRAS 18361-0627, IRAS 18414-0339 and IRAS 19474+2637) with the VLA D configuration. We found that these objects have hundreds of solar masses in dense gas with rotation temperatures from 8 to 27K. No 1.3cm continuum emission was detected at an rms of ∼0.7mJy in all sources except IRAS 18361-0627. We identified 60 clumps and determined their physical parameters (e.g. line width, rotation temperature, size, and mass). The clump masses range from 0.1M_☉ to 4800M_☉. The average size, line width and temperature are 0.1±0.06pc, 1.3±0.4km/s and 16±5K. The discrepancy between NH₃3 and (sub)mm continuum emission is found in IRAS 18196-1331. This phenomenon could occur as a result of the NH₃3 abundance variation being affected by the UV illumination.