64 th International Symposium on Molecular Spectroscopy HCO

64 th International Symposium on Molecular Spectroscopy HCO+ in the Helix Nebula Lindsay N. Zack Lucy M. Ziurys Department of Chemistry Department of Astronomy Steward Observatory Arizona Radio Observatory University of Arizona June 25, 2009

64 th International Symposium on Molecular Spectroscopy Planetary Nebulae • Glowing shell of gas and plasma formed by low to intermediate mass stars in their final stage of evolution • Strong UV radiation field from central star • Shapes and sizes vary June 25, 2009

June 25, 2009 64 th International Symposium on Molecular Spectroscopy Chemistry in Planetary Nebulae • Strong UV field should destroy molecules in PNe • Several molecules have been detected in young PNe • Primarily ions and radicals • Survival in clumps of gas and dust? Molecules Identified in PNe CO CN CCH N 2 H+ HCN CH H 2 CH+ HNC OH HCO+ H 2 O H 2 CO C 2 H 2 CO+ N 2 H+ CS C 2 H C 3 H 2 Si. S Tenenbaum et al. , in preparation

June 25, 2009 64 th International Symposium on Molecular Spectroscopy The Helix Nebula Age: ~12, 000 years Distance: ~200 pc Angular Size: ~1000” • Very old • Lots of dust and gas • • Atomic gas : Ha, N II, O I, C I Molecular gas: CO and vibrationally excited H 2 • Interesting structure • Cometary globules

64 th International Symposium on Molecular Spectroscopy June 25, 2009 CO (J = 2 -1) Map of the Helix Multiple Velocity Components Young et al. 1999

64 th International Symposium on Molecular Spectroscopy June 25, 2009 Why HCO+ ? • m = 3. 89 D • High critical density (ncr ~ 105 cm-3) indicates that HCO+ emission is present in dense gas around the Helix – CO: m = 0. 11 D; ncr ~ 103 cm-3 • Dense gas is shielding and can preserve molecules

64 th International Symposium on Molecular Spectroscopy Mapping the Helix in June 25, 2009 + HCO Goals… • Complete a fully sampled map in HCO+ (J = 1 -0) • Identify “new” clumps of dense gas that may be chemically interesting • Examine the kinematic structure of the Helix • Determine density and temperature distributions • Model HCO+ densities with LVG analysis • Examine chemistry of old PN in detail

June 25, 2009 64 th International Symposium on Molecular Spectroscopy HCO+ Observations KP 12 m • ARO 12 m on Kitt Peak • HCO+ (J = 1 -0) 89. 18853 GHz • Optimal project for new ALMAtype Band 3 receiver – Tsys < 200 K The Map Ø Ø Ø 1000″ x 800″ region 35″ spacing (half beam-size) 775 positions total 500 k. Hz resolution filterbanks 3 s rms noise level < 20 m. K

64 th International Symposium on Molecular Spectroscopy June 25, 2009 Further Observations • ARO SMT on Mt. Graham • HCO+ (J = 3 -2) 267. 5576 GHz • ALMA-type Band 6 receiver Examine select positions in the Helix and compare to J = 1 -0 transition SMT

June 25, 2009 64 th International Symposium on Molecular Spectroscopy HCO+ J = 1 -0 (125, 185) (-15, 270) (390, -30) (130, -180) (-120, 240) (-372, 0) (-240, -100) (-300, -200)

June 25, 2009 64 th International Symposium on Molecular Spectroscopy Helix Nebula (NGC 7293) HCO+ J=1→ 0 ü ~16% complete ü 125 positions finished ü 3 s rms noise level < 20 m. K Beam Size (70″) CO J = 1 → 0 Young et al. 1999

64 th International Symposium on Molecular Spectroscopy June 25, 2009

64 th International Symposium on Molecular Spectroscopy June 25, 2009 Summary • Chemistry in evolved planetary nebulae is more active and complex than originally thought • Presence of HCO+ (J = 3 -2) indicates that very dense gas clumps exist in the Helix • HCO+ (J = 1 -0) is widespread across the Helix and can be used to identify more chemically interesting areas

64 th International Symposium on Molecular Spectroscopy June 25, 2009 Acknowledgements • Dr. Lucy Ziurys • Dr. De. Wayne Halfen • Ziurys Group: Robin Pulliam, Emmy Tenenbaum, Ming Sun, Gilles Adande, Jessica Dodd, Jie Min, Matthew Bucchino, Brent Harris • ARO operators, engineers, and staff • Funding: NASA and NSF