Observations of Herbig Ae disks with nulling interferometry

We present the results of 10 mu m nulling interferometric observations of 13 Herbig Ae stars using the Magellan I (Baade) and the MMT 6.5 m telescopes. A portion of the observations was completed with the adaptive secondary at the MMT. We have conclusively spatially resolved 3 of the 13 stars, HD 100546, AB Aur, and HD 179218, the latter two recently resolved using adaptive optics in combination with nulling interferometry. For the resolved objects we find that the 10 mu m emitting regions have a spatial extent of 15-30 AU in diameter. We also have some evidence for resolved emission surrounding an additional two stars (V892 Tau and R CrA). For those objects in our study with mid-IR SEDs in the classification of Meeus and coworkers, we find that the group I objects ( those with constant to increasing mid-IR flux) are more likely to be resolved, within our limited sample. This trend is evident in correlations in the inferred disk sizes versus the submillimeter SED slope and disk size versus fractional infrared luminosity of the systems. We explore the spatial distribution and orientation of the warm dust in the resolved systems and constrain physical models that are consistent with their observational signatures.