Issue |
A&A
Volume 389, Number 2, July II 2002
|
|
---|---|---|
Page(s) | 577 - 588 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20020452 | |
Published online | 27 June 2002 |
The threaded molecular clumps of Chamaeleon III*
1
SCFAB, Stockholm Observatory, 106 91 Stockholm, Sweden
2
Observatory, PO Box 14, 00014 University of Helsinki, Finland
3
Alfvén Laboratory, Royal Institute of Technology, 100 44 Stockholm, Sweden
Corresponding author: G. F. Gahm, gahm@astro.su.se
Received:
16
October
2001
Accepted:
22
March
2002
We have mapped large areas in the
complex of molecular clouds with the SEST in 13CO(
) and in
C18O(
). The stronger CO emission coincides with areas of
cold dust emission, which is distributed in long, but thin, wavy
filaments. We identify some 40 clumps of enhanced CO emission in these
filaments. In the southern part of
the clumps are
equidistant along the main zig-zag shaped filament. Here we find two
systems of filaments moving at different radial velocities. At least
part of the zig-zag patterns visible on optical images may be caused
by overlapping filaments. All clumps are small (typically 0.02–0.05
pc in radius), and of small mass (typically
,
when assuming the “standard” C18O/H2 column density ratio).
Also the average number densities are small,
cm-3, and the density contrast between clump
and interclump gas is only ~10. In addition the values of
are unusually small, 0.03–0.33. These
clumps have smaller masses than those so far identified in other
molecular clouds. Previously
reported clumps of larger masses in
turn out to be
composed of assemblies of clumps. There are no signs of star formation
in
(unlike
and
), and our
results indicate also that such activity is not expected. However,
with the velocity dispersion of 0.2 km s-1 the clumps would
leave the thin filaments on short timescales, and if the clumps as
such are not confined by some external force, they would also lose
their identity on even shorter timescales. We discuss the possibility
that the clumps are confined by electromagnetic forces, and show that
this may work with reasonable assumptions on the required magnetic
field strength. We also discuss the possibility that the clumps are
attached to magnetic ropes along the filamentary axis, in which case
the clumps could swing back and forth perpendicularly to the axis,
like they were threaded on elastic strings.
Key words: ISM: clouds / ISM: structure
© ESO, 2002
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