Fig. 1.

IR extinction laws compiled from the literature. Red stars plot A _λ /A_Ks toward the GC based on H lines (Fritz et al., 2011). Blue triangles are derived from stars toward the GC (RL85). Green squares are derived from the red clump giants toward the GC (Nishiyama et al., 2009). Cyan diamonds are the Galactic plane average extinction at ǀlǀ < 5° and ǀbǀ < 2° (Gao et al., 2009). The other three kinds of symbols plot the extinction laws obtained from sightlines away from the GC. For comparison, the extinction curves calculated from the interstellar grain model (WD01) for R_V = 3.1 (black solid line) and R_V = 5.5 (black dot-dashed line) are also shown.