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Session 58 - Stellar Modelling/Abundances.
Display session, Wednesday, June 12
The importance of M stars in the integrated light of early-type galaxies is evidenced through the TiO bands seen in the spectra of these galaxies. Recent models of the Galactic bulge, which has been shown to have an integrated spectrum similar to that of a ``typical'' elliptical galaxy, indicate that the M giants there contribute approximately 10% of the V-band flux and greater than half of the light in the K-band. Since our goal is the population synthesis of galaxies, we have constructed a grid of synthetic spectra of early-M (M0--M5) giants. These spectra span wavelengths from the optical (4000 Åto the near-infrared (2.5 \mum) and have been tested through a direct comparison to observed spectra of stars with known effective temperature, surface gravity and metal abundance. A special emphasis has been placed upon modelling the TiO bands. Colors have been derived from the synthetic spectra and pseudo-equivalent widths have been measured for the TiO bands, the near-infrared CO(2-0) and CO(3-0) bands, and a variety of atomic lines. A comparison is made to the trends seen in the strengths of these spectral features as a function of color in nearby M giants. Using recently calculated isochrones, the integrated colors and spectra of some simple stellar populations are also presented.
Program listing for Wednesday