Volume 405, Number 2, July II 2003
|Page(s)||531 - 550|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||19 June 2003|
Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago, 75014 Paris, France
2 Observatoire de Strasbourg, UMR 7550, 11 rue de l'Université, 6700 Strasbourg, France
3 Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
Corresponding author: M. Schultheis, firstname.lastname@example.org
Accepted: 20 March 2003
We present near-IR spectra (HK-band) of a sample of 107 sources with mid-IR excesses at 7 and 15m detected during the ISOGAL survey. Making use of the DENIS interstellar extinction map from Schultheis et al. (1999) we derive luminosities and find that the Mbol vs. and diagrams are powerful tools for identifying supergiants, AGB stars, giants and young stellar objects. The majority of our sample are AGB stars (~80%) while we find four good supergiant candidates, nine young stellar objects and 12 RGB candidates. We have used the most recent relation by Jeong et al. ([CITE]) based on recent theoretical modeling of dust formation of AGB stars to determine mass-loss rates. The mass-loss rates of the supergiants are comparable with those in the solar neighbourhood while the long-period variables cover a mass-loss range from . The red giant candidates lie at the lower end of the mass-loss rate range between . We used the equivalent width of the CO bandhead at 2.3 , the NaI doublet and the CaI triplet to estimate metallicities using the relation by Ramírez et al. ([CITE]). The metallicity distribution of the ISOGAL objects shows a mean dex with a dispersion of which is in agreement with the values of Ramírez et al. ([CITE]) for Galactic Bulge fields between and . A comparison with the solar neighbourhood sample of Lançon & Wood ([CITE]) shows that our sample is ~0.5 dex more metal-rich on average.
Key words: infrared: stars / ISM: dust, extinction / Galaxy: bulge / stars: AGB and post-AGB
© ESO, 2003
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