title: ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-Velocity Bipolar Jets and an Expanding Torus.
abstract: We have mapped12CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with [Formula: see text] resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (>few× 106cm-3), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5 × 10-4M⊙yr-1in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017M⊙) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.
authors.affiliation: Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109, USA.
authors.forename: R
authors.initials: R
authors.lastname: Sahai
authors.affiliation: Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala, Sweden.
authors.forename: W H T
authors.initials: WH
authors.lastname: Vlemmings
authors.affiliation: Centre for Astrohysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK.
authors.forename: T
authors.initials: T
authors.lastname: Gledhill
authors.affiliation: Astrobiology Center (CSIC-INTA), ESAC campus, E-28691 Villanueva de la Canada, Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Sánchez Contreras
authors.affiliation: Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lagrange, France.
authors.forename: E
authors.initials: E
authors.lastname: Lagadec
authors.affiliation: Joint ALMA Observatory (JAO), Alonso de Cordova 3107, Vitacura, Santiago de Chile, and European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile.
authors.forename: L-Å
authors.initials: LÅ
authors.lastname: Nyman
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049, Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Quintana-Lacaci
keywords: AGB and post-AGB — stars; circumstellar matter — stars; individual (IRAS16342-3814) — techniques; interferometric; mass-loss — stars; winds, outflows — stars