Open AccessMethanol masers and their environment at high resolution
Author(s) -
Phillips C. J.,
Norris R. P.,
Ellingsen S. P.,
McCulloch P. M.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.t01-1-01979.x
Subject(s) - physics , maser , astrophysics , telescope , stars , astronomy , galactic plane , star formation , line (geometry) , high resolution , remote sensing , geometry , geology , mathematics
We have used the Australia Telescope Compact Array (ATCA) to make high‐resolution images of the 6.7‐GHz 5 1 → 6 0 A + maser transition of methanol towards 33 sources in the Galactic plane. Including the results from 12 methanol sources in the literature, we find that 17 out of 45 sources have curved or linear morphology. Most of the 17 have a velocity gradient along the line, which is consistent with masers lying in an edge‐on circumstellar disc surrounding a massive star. We also made simultaneous continuum observations of the sources at 8.6 GHz, in order to image any associated H ii region. 25 of the sources are associated with an ultracompact H ii region, with a detection limit of ∼0.5 mJy beam −1 . We argue that the methanol sources without an associated H ii region represent less massive embedded stars, not an earlier stage in the lifetime of the star, as previously suggested.