A mid-infrared imaging survey of proto-planetary nebula candidates

We present the data from a mid-infrared (MIR) imaging survey of 66 proto-pl anetary nebula candidates using two MIR cameras (MIRAC2 and Berkcam) at the NASA Infrared Telescope Facility and the United Kingdom Infrared Telescope . The goal of this survey is to determine the size, flux, and morphology of the MIR emission regions, which sample the inner regions of the circumstel lar dust shells of proto-planetary nebulae. We imaged these proto-planetary nebulae with narrowband filters (Delta lambda/lambda similar to 10%) at wa velengths of notable dust features. With our typical angular resolution of 1", we resolve 17 sources, find 48 objects unresolved, and do not detect on e source. For several sources we checked optical and infrared associations and positions of the sources. In table format, we list the size and flux me asurements for all of the detected objects and show figures of all of the r esolved sources. The proto-planetary nebula candidate sample includes, in a ddition to the predominant proto-planetary nebulae, extreme asymptotic gian t branch stars, young planetary nebulae, a supergiant, and a luminous blue variable. We find that dust shells that are cooler (T similar to 150 K) and brighter in the infrared are more easily resolved. Eleven of the seventeen resolved sources are extended and fall into one of two types of MIR morpho logical classes: core/elliptical or toroidal. Core/elliptical structures sh ow unresolved cores with lower surface brightness elliptical nebulae. Toroi dal structures show limb-brightened peaks suggesting equatorial density enh ancements. We argue that core/ellipticals have denser dust shells than toro idals.