Polycyclic aromatic hydrocarbons openParPAHsclosePar in protoplanetary disks around late-type T Tau stars in Orion Nebular Cluster

We propose a search for farinfrared features from polycyclic aromatic hydrocarbon molecules (PAHs) in a small sample of protoplanetary disks around latetype T Tau stars. These objects were identified in the course of our large SpitzerIRS survey of the Orion A cloud to have midinfrared PAH features with unusual profiles, which are far too bright to explain by photoexcitation by their host stars; they must be excited by ultraviolet light from their more massive neighbors. Recent laboratory spectra of PAHs demonstrate the variation of wavelength and strength with molecule size for the farinfrared features of PAHs, a sensitivity that is lacking in the midinfrared features. The observation of such features in disks around lowmass stars, in which we frequently see the effects of coagulation and growth among the silicategrain population, represents an opportunity to search for size variation among the PAH population, a congruence with the PAH molecules found in the primitive meteorites, and perhaps hints of the role played by carbonaceous molecules in the assembly of solid bodies in disks. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]