Star Counts and Galactic Structure

We use a model of the Galactic stellar distribution to analyse the BATC star count data toward two high Galactic latitude fields. Since star counts at high Galactic latitudes are not strongly related to the radial distribution, they are very suitable for the study of the vertical distribution of the Galaxy. The vertical density distribution of the stars shows the contribution of the thin disc, the thick disc and the stellar halo of the Galaxy. We give quantitative descriptions of these components in terms of exponential discs and a de Vaucouleurs halo. We find that the observed counts support an axial ratio of c/a ~ 0.5, implying a more flattened halo. We consider that it is possible that the halo has two subpopulations, i.e. a flattened inner halo and a spherical outer halo in the Milky Way.