Dense gas in nearby galaxies X.
Dense gas in nearby galaxies
X. interstellar 12C/13C ratios
in the central regions of M82 and IC342
-
C. Henkel
-
Max-Planck-Institut für Radioastronomie
- Auf dem Hügel 69, D-53121 Bonn, Germany
-
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
-
R. Mauersberger
-
Steward Observatory,
The University of Arizona
- Tucson,
AZ 85721, U.S.A.
-
J.B. Whiteoak
-
Paul Wild Observatory,
Australia Telescope National Facility,
CSIRO
- Locked Bag 194, Narrabri NSW 2390, Australia
Paper has been published in January 1998 by the Main Journal of
Astronomy and Astrophysics in its vol. 329, pp. 443 - 450.
If you want to have a look at the complete paper, please click
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Abstract.
12C/13C line intensity ratios have been derived from
several carbon-bearing molecules to confine the range of carbon and oxygen
isotope abundance ratios toward the nuclear regions of two infrared bright
galaxies.
The most stringent limits are obtained from CN mm-wave emission lines.
Supplementary measurements toward the Galactic center region indicate that
overall I(12CN)/I(13CN) line intensity
ratios are giving lower limits to the corresponding
12C/13C abundance ratio.
Toward M82 and IC342, we find 12C/13C > 40 and >30.
Therefore the smaller 12C/13C ratio of our own Galactic
center region (25) may not be typical for central regions of galaxies which are
more luminous in the infrared.
The 12C/13C limits and data from various isotopic species
of CO also infer 16O/18O abundance ratios of > 90 and
> 125 for M82 and IC342, respectively.
From the I(HC14N)/I(HC15N) line intensity
ratio, 14N/15N > 100 is derived for M82.
Any suggestion or comments please
e-mail to einmann@asiaa.sinica.edu.tw.
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