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A&A Supplement Ser., Vol. 124, August, 385-395
Received July 29; accepted November 26, 1996
Studies of dense cores in regions of massive star formation
V. Structure and kinematics of dense cores from ammonia
observations
I. Zinchenko
-
Th. Henning
-
K. Schreyer
Send offprint request: I. Zinchenko
Institute of Applied Physics of the Russian Academy of Sciences,
46 Uljanov str., 603600 Nizhny Novgorod, Russia
Helsinki University Observatory, Tähtitorninmäki, P.O. Box 14,
FIN-00014 University of Helsinki, Finland
Max Planck Society, Research Unit ``Dust in star-forming regions'',
Schillergäßchen 3, D-07745 Jena, Germany
Abstract:
We present results of the observations of 17 molecular clouds
associated with bright FIR sources in the 
(1, 1) and (2, 2) lines
with the 100-m radio telescope in Effelsberg. The lines were detected in
11 clouds and 10 of them have been mapped in these lines. The kinetic
temperatures, sizes, masses and mean densities of the ammonia cores
have been derived.
For most of the detected clouds the masses derived under the assumption
of a relative ammonia abundance of 
are close to virial masses. However, in S 88 B the ratio 
is only 
and in a few other cases this ratio is significantly lower than unity
which may indicate ammonia underabundance. Almost all objects
with the signs of underabundance are among the most
luminous IR sources in our sample.
Most of the mapped cores are elongated with
noticeable velocity gradients along the major axis. The most prominent
example is S 255. S 87 has a two-component structure with 2 distinct
velocity components which overlap partly spatially.
In about half of the mapped sources the 
line widths increase
near the peaks of the ammonia emission.
The kinetic temperatures are centrally peaked. They reach 
in
the centre and drop to 
at the edges of the ammonia emitting
regions.
In S 76 E a weak extended emission in the (1, 1) line at the velocity
blue-shifted by 
relative to the core emission was
detected. Hyperfine intensity anomalies in the (1, 1) transition were found
in S 199 in addition to the known case of these anomalies in S 87.
keywords: stars: formation -- ISM: clouds -- ISM: molecules -- radio lines: interstellar
SIMBAD Objects
Tables at the CDS
web@ed-phys.fr