Methanol masers and millimetre lines: a common origin in protostellar envelopes
Paper i proceeding, 2012

To understand the origin of the CH3OH maser emission, we map the distribution and excitation of the thermal CH3OH emission in a sample of 14 relatively nearby (<6 kpc) high-mass star forming regions that are identified through 6.7 GHz maser emission. The images are velocity-resolved and allow us to study the kinematics of the regions. Further, rotation diagrams are created to derive rotation temperatures and column densities of the large scale molecular gas. The effects of optical depth and subthermal excitation are studied with population diagrams. For eight of the sources in our sample the thermal CH3OH emission is compact and confined to a region <0.4 pc and with a central peak close (<0.03 pc) to the position of the CH3OH maser emission. Four sources have more extended thermal CH3OH emission without a clear peak, and for the remaining two sources, the emission is too weak to map. The compact sources have linear velocity gradients along the semi-major axis of the emission of 0.3 – 13 kms−1 pc−1. The rotation diagram analysis shows that in general the highest rotation temperature is found close to the maser position. The confined and centrally peaked CH3OH emission in the compact sources indicates a single source for the CH3OH gas and the velocity fields show signs of outflow in all but one of the sources. The high detection rate of the torsionally excited v t = 1 line and signs of high-K lines at the maser position indicate radiative pumping, though the general lack of measurable beam dilution effects may mean that the masing gas is not sampled well and originates in a very small region.

stars: formation

ISM: jets and outflows

ISM: kinematics and dynamics


ISM: molecules



Karl Torstensson

Joint Institute for VLBI in Europe (JIVE)

Universiteit Leiden

H.J. van Langevelde

Universiteit Leiden

Joint Institute for VLBI in Europe (JIVE)

F. F. S. van der Tak

Netherlands Institute for Space Research (SRON)

Rijksuniversiteit Groningen

Wouter Vlemmings

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

L. Kristensen

Universiteit Leiden

S. Bourke

Joint Institute for VLBI in Europe (JIVE)

A. Bartkiewicz

Uniwersytet Mikolaja Kopernika

Proceedings of the International Astronomical Union

1743-9213 (ISSN) 1743-9221 (eISSN)

Vol. 8 5287 146-150
978-110703284-2 (ISBN)

The XXVIIIth General Assembly of the International Astronomical Union (IAU)
Beijing, China,


Astronomi, astrofysik och kosmologi


Grundläggande vetenskaper



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