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We report the results of a pilot multiwavelength survey in the radiocontinuum (X, Ka and Q bands, i.e., from 3.6 cm to 7 mm) carried out with theEVLA in order to confirm the presence of very large dust grains in dusty disksand torii around the central stars in a small sample of post-AGB objects, asinferred from millimeter and sub-millimeter observations. Supporting mm-waveobservations were also obtained with CARMA towards three of our sources. OurEVLA survey has resulted in a robust detection of our most prominent submmemission source, the pre-planetary nebula IRAS 22036+5306, in all three bands,and the disk-prominent post-AGB object, RV Tau, in one band. The observedfluxes are consistent with optically-thin free-free emission, and since theyare insignificant compared to their submm/mm fluxes, we conclude that thelatter must come from substantial masses of cool, large (mm-sized) grains. Wefind that the power-law emissivity in the cm-to-submm range for the largegrains in IRAS22036 is nu^{beta}, with beta=1-1.3. Furthermore, the value ofbeta in the 3 to 0.85 mm range for the three disk-prominent post-AGB sources(beta < or = 0.4) is significantly lower than that of IRAS22036, suggestingthat the grains in post-AGB objects with circumbinary disks are likely largerthan those in the dusty waists of pre-planetary nebulae.

An evla and carma study of dusty disks and torii with large grains in dying stars