A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Preplanetary Nebula IRAS 22036+5306

Abstract

We report high angular resolution (~1) CO J = 3-2 interferometric mapping using the Submillimeter Array (SMA) of IRAS 22036+5306 (I22036), a bipolar preplanetary nebula (PPN) with knotty jets discovered in our HST snapshot survey of young PPNs. In addition, we have obtained supporting lower resolution (~10) CO and ^(13)CO J = 1-0 observations with the Owens Valley Radio Observatory (OVRO) interferometer, as well as optical long-slit echelle spectra at the Palomar Observatory. The CO J = 3-2 observations show the presence of a very fast (~220 km s^(-1)), highly collimated, massive (0.03 M_☉) bipolar outflow with a very large scalar momentum (about 10^(39) g cm s^(-1)), and the characteristic spatiokinematic structure of bow shocks at the tips of this outflow. The Hα line shows an absorption feature blueshifted from the systemic velocity by ~100 km s-1, which most likely arises in neutral interface material between the fast outflow and the dense walls of the bipolar lobes at low latitudes. The fast outflow in I22036, as in most PPNs, cannot be driven by radiation pressure. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I22036, implying a very substantial mass (0.02-0.04 M_☉) of large (radius gtrsim1 mm), cold (≲50 K) dust grains associated with I22036's toroidal waist. We also find that the 13C/12C ratio in I22036 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 extended dust shell and the torus) and the high ^(13)C/^(12)C ratio in I22036 provides strong support for this object having evolved from a massive (≳4 M_☉) progenitor in which hot-bottom-burning has occurred.