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Methanol masers and millimetre lines: a common origin in protostellar envelopes

Published online by Cambridge University Press:  24 July 2012

Karl J. E. Torstensson ,
Huib Jan van Langevelde ,
Floris F. S. van der Tak ,
Wouter H. T. Vlemmings ,
Lars E. Kristensen ,
Stephen Bourke  and
Anna Bartkiewicz
Karl J. E. Torstensson
Affiliation:
Joint Institute of VLBI in Europe, PO Box 2, NL-7990 AA Dwingeloo, The Netherlands email: [email protected] Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands email: [email protected]
Huib Jan van Langevelde
Affiliation:
Joint Institute of VLBI in Europe, PO Box 2, NL-7990 AA Dwingeloo, The Netherlands email: [email protected] Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands email: [email protected]
Floris F. S. van der Tak
Affiliation:
SRON Netherlands Institute for Space Research, Landleven 12, NL-9747 AD Groningen, The Netherlands email: [email protected] Kapteyn Astronomical InstituteUniversity of Groningen, The Netherlands
Wouter H. T. Vlemmings
Affiliation:
Chalmers University of Technology, Department of Earth and Space Science, SE-412 96 Gothenburg, Sweden email: [email protected]
Lars E. Kristensen
Affiliation:
Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands email: [email protected]
Stephen Bourke
Affiliation:
Joint Institute of VLBI in Europe, PO Box 2, NL-7990 AA Dwingeloo, The Netherlands email: [email protected]
Anna Bartkiewicz
Affiliation:
Toruń Centre for Astronomy, Nicolaus Copernicus University, Gagarina 11, 87-100 Toruń, Poland email: [email protected]
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Abstract

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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 vt = 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.

Keywords

Masersstars: formationISM: jets and outflowsISM: kinematics and dynamicsISM: moleculessubmillimeter
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S287: Cosmic Masers - from OH to H0 , January 2012 , pp. 146 - 150
Copyright
Copyright © International Astronomical Union 2012

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