Modeling Fermi-LAT Observations of Diffuse Gamma-Ray Emission in the Galactic Center

The Fermi-Large Area Telescope completed its checkout phase in early August 2008 and began a planned one-year survey of the sky in the 30 MeV-300 GeV range. The most-prominent feature of the GeV sky is the bright band of diffuse emission around the Galactic equator. This Galactic foreground, from interactions of cosmic rays with interstellar gas and photons, is brightest in the range |l| < 15°. This region of the sky is of intense interest for gamma-ray astrophysics but its diffuse emission is difficult to model accurately. The principal difficulties are the lack of kinematic distance discrimination in spectral line surveys of the interstellar medium, the uncertain W(CO)/N(H₂) ratio and spin temperature and optical depth corrections for N(H I), and uncertain cosmic-ray densities. Approaches to address the challenges in the Galactic center region, informed by the accumulated LAT observations from the sky survey, will be described.