Galaktik Astronomi Çalıştayı Bildiriler Kitabı
The Role of the Stellar Chemical Evolution Models in Galactic ResearchTolgahan Kılıçoğlu
Galactic chemical abundance gradients may help us to understand the formation and evolution of galaxies. Early-B and late-F type stars are often used to construct these gradients, because the photosphere of these stars is generally well-mixed by convection or stellar wind. The photosphere of the other stars might be affected by diffusion and their spectral features may also be disturbed by magnetic field or strong wind. It is essential to use realistic model atmospheres for each spectral type to obtain reliable chemical abundances. This paper first reviews the assumptions of the current model atmosphere codes and gives some examples of their bad impacts on the chemical abundances. The concept of diffusion and its related parameters are briefly explained. Some abundance analysis results are given to compare with the prediction of the current diffusion models. Current theories on the strong magnetic field of the early type chemically peculiar single stars have been discussed. Some possible solutions are suggested to take account for magnetic field and stellar wind for the the abundance analysis. A late type star with a moderate magnetic field and an early type star with a strong wind are given as examples to see how biased the derived abundances are.