Galactic mass-losing AGB stars probed with the IRTS. I

• Published in: Astronomy and astrophysics (Berlin) 2001-09, Vol.376 (3), p.997-1010
• Main Authors: Le Bertre, T., Matsuura, M., Winters, J. M., Murakami, H., Yamamura, I., Freund, M., Tanaka, M.
• Format: Article
• Language: English
• Subjects: galaxy: solar neighbourhood; infrared: stars; ISM: evolution; stars: AGB and post-AGB; stars: carbon; stars: mass-loss
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20011033

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$^{-6} M_{\odot}$ yr-1.