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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2003

Near-IR spectra of ISOGAL sources in the Inner Galactic Bulge

M. Schultheis
A. Lançon
  • Fonction : Auteur
F. Schuller
  • Fonction : Auteur
D. K. Ojha
  • Fonction : Auteur

Résumé

In this work we present near-IR spectra (HK-band) of a sample of 107 sources with mid-IR excesses at 7 and 15 $\\rm \\mu$m 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 $\\rm M_{bol}$ vs.~$\\rm ^{12}CO$ and $\\rm M_{bol} vs. H_{2}O$ 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 $\\rm K_{0}-[15]$ relation by Jeong et al. (2002) based on recent theoretical modeling of dust formation of AGB stars to determine mass-loss rates. However, the uncertainties in the mass-loss rates are rather large. 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 $\\rm -5 < log \\dot{\\it{M}} < -7$. The red giant candidateslie at the lower end of the mass-loss rate range between $\\rm -6.5 < log \\dot{{\\it{M}}} < -9$. We used the equivalent width of the CO bandhead at 2.3 $\\rm \\mu m$, the NaI doublet and the CaI triplet to estimate metallicities using the relation by Ram\\\'{\\i}rez et al. (\\cite{Ramirez2000}). The metallicity distribution of the ISOGAL objects shows a mean [Fe/H] $\\sim$ -0.25 dex with a dispersion of $\\rm \\pm 0.40 dex$ which is in agreement with the values of Ram\\\'{i}rez et al. (\\cite{Ramirez2000}) for Galactic Bulge fields between $\\rm b = -4^{o}$ and $\\rm b = -1.3^{o}$. A comparison with the solar neighbourhood sample of Lan\çon & Wood (LW) shows that our sample is ~ 0.5 dex more metal-rich on average.

Dates et versions

hal-00005422 , version 1 (16-06-2005)

Identifiants

Citer

M. Schultheis, A. Lançon, A. Omont, F. Schuller, D. K. Ojha. Near-IR spectra of ISOGAL sources in the Inner Galactic Bulge. Astronomy and Astrophysics - A&A, 2003, 405, pp.531-550. ⟨hal-00005422⟩
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