VLA observations of water masers towards 6.7 GHz methanol maser sources

Abstract

22 GHz water and 6.7 GHz methanol masers are usually thought as signposts of early stages of high-mass star formation but little is known about their associations and the physical environments they occur in. The aim was to obtain accurate positions and morphologies of the water maser emission and relate them to the methanol maser emission recently mapped with Very Long Baseline Interferometry. A sample of 31 methanol maser sources was searched for 22 GHz water masers using the VLA and observed in the 6.7 GHz methanol maser line with the 32 m Torun dish simultaneously. Water maser clusters were detected towards 27 sites finding 15 new sources. The detection rate of water maser emission associated with methanol sources was as high as 71%. In a large number of objects (18/21) the structure of water maser is well aligned with that of the extended emission at 4.5 $\mu$m confirming the origin of water emission from outflows. The sources with methanol emission with ring-like morphologies, which likely trace a circumstellar disk/torus, either do not show associated water masers or the distribution of water maser spots is orthogonal to the major axis of the ring. The two maser species are generally powered by the same high-mass young stellar object but probe different parts of its environment. The morphology of water and methanol maser emission in a minority of sources is consistent with a scenario that 6.7 GHz methanol masers trace a disc/torus around a protostar while the associated 22 GHz water masers arise in outflows. The majority of sources in which methanol maser emission is associated with the water maser appears to trace outflows. The two types of associations might be related to different evolutionary phases.

accepted by Astronomy & Astrophysics

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Cited by in corpus (13)

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• A Water Maser and Ammonia Survey of GLIMPSE Extended Green Objects (EGOs)
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• Periodic variability of 6.7GHz methanol masers in G22.357+0.066
• A search for water masers associated with class II methanol masers - I. Longitude range 6 to 20 degrees
• Discovery of periodic class II methanol masers associated with G339.986-0.425 region
• Bursting Activity in a High-Mass Star-Forming Region G33.64-0.21 Observed with the 6.7 GHz Methanol Maser
• Testing the Hypothesis that Methanol Maser Rings Trace Circumstellar Disks: High Resolution Near-IR and Mid-IR Imaging
• Probing the magnetic fields of massive star forming regions with methanol maser polarisation
• Orientation effect on the ligh curve shape of periodic methanol maser sources
• Milliarcsecond structure of water maser emission in two young high-mass stellar objects associated with methanol masers
• Simultaneous 22 GHz Water and 44 GHz Methanol Masers Survey of Ultracompact HII Regions
• Detections of Compact Radio Continuum toward Methanol Maser Rings Using the VLA