Submillimeter structure of the disk of the Butterfly Star

We present a spatially resolved 894 mm map of the circumstellar disk of the Butterfly Star in Taurus ( IRAS 04302 + 2247), obtained with the Submillimeter Array (SMA). The predicted and observed radial brightness profiles agree well in the outer disk region but differ in the inner region with an outer radius of similar to 80-120 AU. In particular, we find a local minimum of the radial brightness distribution at the center, which can be explained by an increasing density/optical depth combined with the decreasing vertical extent of the disk toward the center. Our finding indicates that young circumstellar disks can be optically thick at wavelengths as long as 894 mm. While earlier modeling lead to general conclusions about the global disk structure and, most importantly, evidence for grain growth in the disk ( Wolf, Padgett, & Stapelfeldt), the presented SMA observations provide more detailed constraints for the disk structure and dust grain properties in the inner, potentially planet-forming region (less than or similar to 80-120 AU) versus the outer disk region (similar to 120-300 AU).