Issue |
A&A
Volume 448, Number 2, March III 2006
|
|
---|---|---|
Page(s) | 597 - 611 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20054275 | |
Published online | 24 February 2006 |
The magnetic field in the star-forming region Cepheus A
from H2O maser polarization observations
1
Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire, SK11 9DL, UK e-mail: wouter@jb.man.ac.uk
2
Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
3
Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
4
Instituto de Ciencias del Espacio (CSIC)-IEEC, C/ Gran Capitá, 2-4, 08034 Barcelona, Spain
Received:
29
September
2005
Accepted:
13
October
2005
We present linear and circular polarization observations of
the H2O masers in 4 distinct regions spread over 1 2 arcsec around the HW2 high-mass young stellar object in the Cepheus A star-forming region. We find magnetic fields between
100–600 mG in the central maser region, which has been argued to
trace a circumstellar disk. The masers further from HW2 have field
strengths between 30–100 mG. In all cases the magnetic field
pressure is found to be similar to the dynamic pressure, indicating
that the magnetic field is capable of controlling the
outflow dynamics around HW2. In addition to several H2O maser
complexes observed before, we also detect a new maser filament,
1″ (
690 AU) East of HW2, which we
interpret as a shocked region between the HW2 outflow and the
surrounding medium. We detect a linear polarization gradient along
the filament as well as a reversal of the magnetic field
direction. This is thought to mark the transition between the
magnetic field associated with the outflow and that found in the
surrounding molecular cloud. In addition to the magnetic field we
determine several other physical properties of the maser region,
including density and temperatures as well as the maser beaming
angles.
Key words: star: formation / masers / polarization / magnetic fields
© ESO, 2006
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