Large grains in the Orion Nebula's circumstellar disks

摘要

We present a lambda = 4.05 mu m image of the largest proplyd silhouette disk in Orion, 114-426, using NIRSPEC at the Keck Observatory. The diameter of the disk at 4 mu m is only marginally smaller than that observed in the optical with HST. This may be the first signature of a turnover in the extinction curve for the translucent but gray opacity of the outer disk, suggesting that absorption in the NIR is dominated by large processed grains with sizes slightly larger than similar to 4 mu m. Implications for planet formation in the Orion proplyds are discussed.