Poster Title: Near-IR spectroscopy in the Inner Galactic Bulge
Abstract: 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 ($\sim$ 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.
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. (2000). 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. (2000) for Galactic Bulge fields between $\rm b = -4^{o}$ and $\rm b = -1.3^{o}$.
We present a comparison between observed spectra to a grid of synthetic spectra based on hydrostatic MARCS models. We discuss the influence of $\rm T_{eff}$, log\,g, mass and metallicity on the different observed spectral features and do a first quantitative comparison between observed and synthetic spectra for different metallicities.
Link to poster: N/A