Radio Study of Protostars

We report radio continuum and spectral line observations of five MYSOs namely: G310.0135+00.3892, G339.8838-01.2588, G332.9868-00.4871, G345.4938+01.4677 and G345.5043+00.3480. The objects were selected from the Red MSX Source (RMS) survey based on their bolometric luminosities and distances and were observed with the Australia Telescope Compact Array (ATCA). Results from the ATCA observations were compared to the H2O southern Galactic Plane Survey (HOPS) data, extracted using the galactic coordinates of the various objects. G345.5043+00.3480 was not detected probably because it was too extended. The observation using ATCA was carried out at 24.5 GHz observing frequency in the 1.5 km array configuration mode, achieving a resolution of ∼ 2 arcsec with a sensitivity range of σ ∼ 0.10 − 0.58 mJy/beam for the objects. The radio continuum results were compared with previous studies by Purser (2017) for the same objects using ATCA at 22.8 GHz in the 6 km array configuration mode, achieving a resolution of 0.5 arcsec and sensitivity of σ ∼ 73 − 106 μJy/beam for the objects. The luminosities of the objects were determined in the range of 1.87×10 12 - 2.00×10^(13) W. From the spectral line emission, we report the detection of water masers in all science targets with spectral luminosities of the water masers in the range of 0.11 − 2.80 × 10^(−6) L. The water masers detected in the sources were offset on average by ∼ 2 km/s from the known local standard of rest velocity of the MYSO. The reported luminosities (0.11 − 2.80 × 10^(−6) L) of the water masers were found to be in the circumstellar region of the MYSOs where water masers are found to have a luminosity in the order of 10^(−6) L (Lo, 2005). In addition,multiple emission peaks were observed in the objects. The multiple water maser spots suggest the likely presence of several water masers not spatially co-located caused by the collision of the water masers and the jet around the core of the forming MYSO. On the other hand, NH3 (2,2) in G345.4938+01.4677 was detected mapping out the cold dense region of the emission.