Molecular abundances in the Magellanic Clouds I.
Molecular abundances in the Magellanic Clouds
I. A multiline study of five cloud cores
-
Y.-N. Chin
-
Institute of Astronomy & Astrophysics,
Academia Sinica
- P.O. Box 1-87 Nankang, 115 Taipei, Taiwan
- and
-
Radioastronomisches Institut der Universität Bonn
- Auf dem Hügel 71, D-53121 Bonn, Germany
-
C. Henkel
-
Max-Planck-Institut für Radioastronomie
- Auf dem Hügel 69, D-53121 Bonn, Germany
-
J.B. Whiteoak
-
Paul Wild Observatory,
Australia Telescope National Facility,
CSIRO
- Locked Bag 194, Narrabri NSW 2390, Australia
- T.J. Millar
-
Department of Physics,
UMIST
- PO Box 88, Manchester M60 1QD, United Kingdom
- M.R. Hunt
-
University of Western Sydney Nepean
- P.O. Box 10, Kingswood, NSW 2747, Australia
- C. Lemme
-
Max-Planck-Institut für Radioastronomie
- Auf dem Hügel 69, D-53121 Bonn, Germany
- and
-
Institut für Planetenerkundung,
DLR
- Rudower Chaussee 5, D-12489 Berlin, Germany
Paper published in January 1997 by the Main Journal of
Astronomy and Astrophysics in Vol. 317, pp. 548 - 562.
If you want to have a look at the complete paper please click
here (PostScript file of 1779264 bytes).
Abstract.
Nine HII regions of the LMC were mapped in
13CO(1-0) and three in 12CO(1-0) to study the physical
properties of the interstellar medium in the Magellanic Clouds.
For N113 the molecular core is found to have a peak position which differs
from that of the associated HII region by 20.
Toward this molecular core the 12CO and 13CO peak
TMB line temperatures of 7.3 K and 1.2 K are the highest
so far found in the Magellanic Clouds.
The molecular concentrations associated with N113, N44BC, N159HW, and N214DE
in the LMC and LIRS36 in the SMC were investigated in a variety of molecular
species to study the chemical properties of the interstellar medium.
I(HCO+)/I(HCN) and I(HCN)/I(HNC) intensity ratios
as well as lower limits to the I(13CO)/I(C18O) ratio
were derived for the rotational 1-0 transitions.
Generally, HCO+ is stronger than HCN, and HCN is stronger than HNC.
The high relative HCO+ intensities are consistent with a
high ionization flux from supernovae remnants and young stars,
possibly coupled with a large extent of the HCO+ emission region.
The bulk of the HCN arises from relatively compact dense cloud cores.
Warm or shocked gas enhances HCN relative to HNC.
From chemical model calculations it is predicted that I(HCN)/I(HNC)
close to one should be obtained with higher angular resolution
(>~ 30) toward the cloud cores.
Comparing virial masses with those obtained from the integrated CO intensity
provides an H2 mass-to-CO luminosity conversion factor of
1.8 × 1020 mol cm-2 (K*kms)-1 for N113 and
2.4 × 1020 mol cm-2 (K*kms)-1 for N44BC.
This is consistent with values derived for the Galactic disk.
Any suggestion or comments please
e-mail to einmann@asiaa.sinica.edu.tw.
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