Issue |
A&A
Volume 376, Number 3, September IV 2001
|
|
---|---|---|
Page(s) | 997 - 1010 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011033 | |
Published online | 15 September 2001 |
Galactic mass-losing AGB stars probed with the IRTS. I.
1
DEMIRM, UMR 8540, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
2
Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
3
Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
4
UMIST, Department of Physics, PO Box 88, Manchester M60 1QD, UK
5
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
6
Infrared Astrophysics Branch, Code 685, Goddard Space Flight Center, Greenbelt, MD 20771, USA
7
Department of Physics, Catholic University of America, Washington, DC 20064, USA
Corresponding author: T. Le Bertre, Thibaut.LeBertre@obspm.fr
Received:
25
April
2001
Accepted:
12
July
2001
AGB mass-losing sources are easy to identify and to characterize
in the near-infrared range (1-5 μm). We make use of the near-infrared
data acquired by the Japanese space experiment IRTS to study a sample of
sources detected in the 2 celestial strips surveyed by the IRTS. Mass-loss
rates and distances are estimated for 40 carbon-rich sources and
86 oxygen-rich sources of which 8 are probably of S-type. Although the sample
is small, one sees a dependence of the relative contribution of the two kinds
of sources to the replenishment of the interstellar medium (ISM) on
the galactocentric distance. E.g. from 6 to 8 kpc, oxygen-rich sources
in our sample
contribute 10-12 times as much as carbon rich sources, whereas from 10
to 12 kpc, the latters contribute 3-4 times as much as the formers.
Therefore, one would expect a gradient in the composition of the ISM
between 6 and 12 kpc from the Galactic Centre, especially in its dust
component. Most of the replenishment (>50% ) by AGB stars is due to
sources with mass-loss rate larger than 10 yr-1.
Key words: stars: carbon / stars: mass-loss / stars: AGB and post-AGB / ISM: evolution / galaxy: solar neighbourhood / infrared: stars
© ESO, 2001
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