A massive, dusty toroid with large grains in the pre-planetary nebula IRAS22036+5306

Using the Submillimeter Array (SMA), we have obtained high angular-resolution (∼1″) interferometric maps of the submillimeter (0.88 mm) continuum and CO J=3-2 line from IRAS∈22036+5306 (I∈22036), a bipolar pre-planetary nebula (PPN) with knotty jets discovered in our HST SNAPshot survey of young PPNe. In addition, we have obtained supporting lower-resolution (∼10″) 2.6 mm continuum and CO, ¹³CO J=1-0 observations with the Owens Valley Radio Observatory (OVRO) interferometer. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I∈22036, implying a very substantial mass (0.02-0.04M) of large (i.e., radius 1 mm), cold (≲50 K) dust grains associated with I∈22036's toroidal waist. The CO J=3-2 observations show the presence of a very fast (∼220 km∈s^-1), highly collimated, massive (0.03M) bipolar outflow with a very large scalar momentum (about 10³⁹ g∈cm∈s^-1), and the characteristic spatio-kinematic structure of bow-shocks at the tips of this outflow. The fast outflow in I∈22036, as in most PPNe, cannot be driven by radiation pressure. The large mass of the torus suggests that it has most likely resulted from common-envelope evolution in a binary, however it remains to be seen whether or not the time-scales required for the growth of grains to millimeter sizes in the torus are commensurate with such a formation scenario. The presence of the torus should facilitate the formation of the accretion disk needed to launch the jet. We also find that the ¹³C/¹²C ratio in I∈22036 is very high (0.16), close to the maximum value achieved in equilibrium CNO-nucleosynthesis (0.33). The combination of the high circumstellar mass (i.e., in the torus and an extended dust shell inferred from ISO far-infrared spectra) and the high ¹³C/¹²C ratio in I∈22036 provides strong support for this object having evolved from a massive (≳4M) progenitor in which hot-bottom-burning has occurred. © 2007 Springer Science+Business Media B.V.

Duke Scholars

Author Ken H Young Pathology