Stellar density map of the Milky Way

The SEGUE imaging scans allow, for the first time, a comprehensive analysis of Milky Way structure at both high and low latitudes using uniform Sloan Digital Sky Survey photometry. Incorporating photometry of all relevant stars simultaneously, CMD fitting bypasses the need to choose single tracer populations.

Using old stellar populations of differing metallicities as templates, we obtain a sparse three-dimensional map of the stellar mass distribution at |Z|>1kpc. Fitting a smooth Milky Way model comprising exponential thin and thick disks and an axisymmetric power-law halo allows us to constrain the structural parameters of the thick disk and halo. The thick-disk scale height and length are well constrained at 0.75+/-0.07kpc and 4.1+/-0.4kpc, respectively.