Physics
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21442605s&link_type=abstract
American Astronomical Society, AAS Meeting #214, #426.05; Bulletin of the American Astronomical Society, Vol. 41, p.696
Physics
Scientific paper
Pre-planetary nebulae (PPNs), short-lived transition objects between the AGB and Planetary Nebulae (PN) phases, hold the key to understanding how the slowly expanding, largely spherical, circumstellar envelopes (CSEs) of AGB stars transform into highly aspherical PNs with elongated lobes expanding at high speeds. In 1998, Sahai & Trauger proposed that, as stars evolve off the AGB, they drive collimated fast winds that sweep up and shock the AGB CSE, producing the observed dramatic change in circumstellar geometry and kinematics. The PPN, IRAS22036+5306 (I22036) offers an exciting opportunity to test this hypothesis. Its highly structured morphology in HST images, and CO J=3-2 interferometric mapping, show that fast ( 200 km/s), collimated jet-like outflows are actively sculpting the CSE into a bipolar PPN. I22036 is thus a key object in clarifying the physics of the transition to bipolarity at the beginning of post-AGB evolution.
We present the results of a new multiwavelength study of this I22036. New HST Halpha and [OI] emission-line images clearly delineate the active shocks, and deep broad-band images reveal point-symmetric ansae beyond the tips of the main bipolar lobes, an extended round halo representing the remnant AGB CSE, and the central star. Optical long-slit (echelle) spectroscopy with the Keck/ESI shows the detailed kinematical structure of the shocked regions. Near-IR (1.1-2.4 micr) spectroscopy of I22036 using the Palomar 200-inch/TripleSpec spectrograph shows strong H2 (delta-V=1) emission from shocked molecular gas in a bipolar outflow. Prominent CO (delta-V=2) bandheads are seen in emission towards the center, indicating very hot (>few x 1000K) gas in a disk or outflow. We have also obtained VLA measurements of the circular polarisation of OH masers in I22036 in order to probe the line-of-sight magnetic field in this object.
Claussen Mark
Contreras S'anchez C.
Morris Marita
Sahai Raghvendra
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