Modeling the infrared extinction toward the galactic center

We model the similar to 1-19 mu m infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be A(V) similar to 38-42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep similar to 1-3 mu m near-IR extinction and the flat similar to 3-8 mu m mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small R-V and steep near-IR extinction), and dust in dense regions (characterized by large R-V and flat UV extinction).