2010ApJ...723.1418M

We have obtained subarcsecond mid-IR images of a sample of debris disks within 100 pc. For our sample of 19 A-type debris disk candidates chosen for their IR excess, we have resolved, for the first time, five sources plus the previously resolved disk around HD 141569. Two other sources in our sample have been ruled out as debris disks since the time of sample selection. Three of the six resolved sources have inferred radii of 1-4 AU (HD 38678, HD 71155, and HD 181869), and one source has an inferred radius ∼10-30 AU (HD 141569). Among the resolved sources with detections of excess IR emission, HD 71155 appears to be comparable in size (r ∼ 2 AU) to the solar system's asteroid belt, thus joining ζ Lep (HD 38678, reported previously) to comprise the only two resolved sources of that class. Two additional sources (HD 95418 and HD 139006) show spatial extents that imply disk radii of ∼1-3 AU, although the excess IR fluxes are not formally detected with better than 2σ significance. For the unresolved sources, the upper limits on the maximum radii of mid-IR disk emission are in the range ∼1-20 AU, four of which are comparable in radius to the asteroid belt. We have compared the global color temperatures of the dust to that expected for the dust in radiative equilibrium at the distances corresponding to the observed sizes or limits on the sizes. In most cases, the temperatures estimated via these two methods are comparable, and therefore, we see a generally consistent picture of the inferred morphology and the global mid-IR emission. Finally, while our sample size is not statistically significant, we note that the older sources (>200 Myr) host much warmer dust (T ≳ 400 K) than younger sources (in the tens of Myr).