Detection of Extragalactic 15N
The detection of extragalactic 15N:
Consequences for nitrogen nucleosynthesis and chemical evolution
-
Y.-N. Chin
-
Institute of Astronomy & Astrophysics,
Academia Sinica
- P.O. Box 1-87 Nankang, 11529 Taipei, Taiwan
-
C. Henkel
-
Max-Planck-Institut für Radioastronomie
- Auf dem Hügel 69, D-53121 Bonn, Germany
-
N. Langer
-
Institut für Physik,
Universität Potsdam
- Am Neuen Palais 10, D-14469 Potsdam, Germany
-
R. Mauersberger
-
Steward Observatory,
The University of Arizona
- Tucson,
AZ 85721, U.S.A.
Paper published in February 20, 1999 by Astrophysical Journal Letters
in vol. 512, pp. L143 - L146.
If you want to have a look at the preprint, please click
here (PostScript file of 299009 bytes),
here (gzip-compressed PostScript file of 87230 bytes), or
here (PDF file of 79369 bytes).
Abstract
Detections of extragalactic 15N are reported from observations of
the rare hydrogen cyanide isotope HC15N toward the Large
Magellanic Cloud (LMC) and the core of the (post-) starburst galaxy NGC 4945.
Accounting for optical depth effects, the LMC data from the massive
star-forming region N113 infer a 14N/15N ratio of 111
± 17, about twice the 12C/13C value.
For the LMC star-forming region N159HW and for the central region of
NGC 4945, 14N/15N ratios are also ~ 100.
The 14N/15N ratios are smaller than all interstellar
nitrogen isotope ratios measured in the disk and center of the Milky Way,
strongly supporting the idea that 15N is predominantly of
`primary' nature, with massive stars being its dominant source.
Although this appears to be in contradiction with standard stellar evolution
and nucleosynthesis calculations, it supports recent findings of abundant
15N production due to rotationally induced mixing of
protons into the helium-burning shells of massive stars.
Any suggestion or comments please
e-mail to einmann@asiaa.sinica.edu.tw.
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