Issue |
Astron. Astrophys. Suppl. Ser.
Volume 144, Number 1, May II 2000
|
|
---|---|---|
Page(s) | 123 - 140 | |
DOI | https://doi.org/10.1051/aas:2000200 | |
Published online | 15 May 2000 |
Multiline CO observations of MBM 32 *
1
Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
2
I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
Send offprint request to: J.G.A. Wouterloot, e-mail: wouterloot@astro.uni-bonn.de
Received:
5
October
1999
Accepted:
2
February
2000
We present a detailed study of the high latitude cloud MBM 32.
Observations were made in the , (2-1), and (3-2) transitions
of 12CO and in 13CO(1-0) and (2-1). These data were
complemented by 21 cm Hi data and by IRAS 60 and 100 μm data.
Our data show that MBM 32 consists of a main cloud component at
km s-1 (mass about 16.9
), and a smaller
component at
km s-1 (4.1
), in addition
to some emission in between those two velocities (<0.5
).
We study the gas distribution and the CO line ratios within MBM 32, the latter
also along a cut through both cloud components. We find that the ratios of
different rotational transitions are constant within each cloud part. Only
the ratio 12CO(
CO(1-0) is lower in the cloud center.
This suggests equal excitation conditions through MBM32 and line temperatures
determined through clump filling factors.
All CO components show associated Hi emission, but
small velocity differences of typically 1 km s-1 exist between the
Hi and
CO gas. The mass of associated Hi gas is similar to the molecular mass
for all components.
There is a good correlation between FIR, CO, and Hi emission.
The dust mass is about 0.073
, and the ratio of gas and
dust mass (280) is lower than found from similar (IRAS) data
for denser clouds, suggesting that the amount of dust colder than 20 K is
relatively small.
We subdivide the CO data cubes in Gaussian shaped clumps; 40-50% of the
CO emission can be assigned to the larger clumps. The remaining emission
comes from either more extended clumps or from overlapping unresolved
clumps.
Key words: ISM: clouds / ISM: individual objects: MBM 32 / ISM: molecules / radio lines: ISM
© European Southern Observatory (ESO), 2000