Richard Dodson, Charles Moriarty
Methanol masers can provide valuable insight into the processes involved in
high-mass star formation, however the local environment in which they form is
still unclear. Four primary, yet conflicting, models have emerged to explain
the commonly observed methanol maser structures at 6.67 GHz. These suggest that
masers trace accretion disks, outflows, shock fronts or disks dominated by
infall/outflows. One proposed means of testing these models is through mapping
the local magnetic field structures around maser sources, which were predicted
to lie parallel to shock and outflows and perpendicular to accretion disks. To
follow up this suggestion we have determined magnetic field directions from
full polarisation observations of 10 6.67-GHz sources. We find morphology that
is parallel to the source structure, indicative of shocks or outflows, in five
sources and perpendicular morphology indicative of disks in three. These
results do not support any of the expected models and the diverse morphologies
observed indicate that the masers could be emitting from different evolutionary
stages or environments, or from a common local environment with complex
associated magnetic fields. To resolve this conflict we suggest a new approach
that will search the simulations of massive star formation, which are just
becoming available, for suitable sites for maser emission.
View original:
http://arxiv.org/abs/1201.1687
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