We model the { \sim } 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 } } { \sim } 38–42 { mag } .
The limitation of the model , i.e. , its difficulty in simultaneously reproducing both the steep { \sim } 1–3 { \mu m } near-IR extinction and the flat { \sim } 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 ) .