june 21, 2013 68 th international symposium on molecular spectroscopy nicholas r. zeigler lindsay n....
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June 21, 201368th International Symposium on Molecular Spectroscopy
Nicholas R. ZeiglerLindsay N. ZackNeville J. WoolfLucy M. Ziurys Department of Chemistry Department of Astronomy Steward Observatory Arizona Radio Observatory University of Arizona
HCO+ in the Helix Nebula
June 21, 201368th 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 21, 201368th International Symposium on Molecular Spectroscopy
Morphologies
June 21, 201368th 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 , H2,
• Polyatomic molecules: C3H2, H2CO
(Tenenbaum et al 2009)
• Interesting structure• Cometary globules
June 21, 201368th 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 , H2,
• Polyatomic molecules: C3H2, H2CO
(Tenenbaum et al 2009)
• Interesting structure• Cometary globules
Taylor 1977
June 21, 201368th 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 , H2,
• Polyatomic molecules: C3H2, H2CO
(Tenenbaum et al 2009)
• Interesting structure• Cometary globules
O’Dell et al. 2004
June 21, 201368th International Symposium on Molecular Spectroscopy
Globules
June 21, 201368th International Symposium on Molecular Spectroscopy
CO (J = 2-1) Map of the Helix
Young et al. 1999
Multiple Velocity Components
June 21, 201368th International Symposium on Molecular Spectroscopy
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
June 21, 201368th International Symposium on Molecular Spectroscopy
HCO+ Observations
• ARO 12m on Kitt Peak• HCO+ (J = 1-0)
89.18853 GHz• Optimal project for new ALMA-
type Band 3 receiver (84–116 GHz)
– Tsys < 200 K
– rms noise < 20 mK• Map across entire Helix
(~1000” x ~800”)
KP 12m
June 21, 201368th International Symposium on Molecular Spectroscopy
• 35″ spacing
• 129 positions
Beam Size (70″)
• 70″ spacing• 89 positions
Integration time ~2-3 hours
June 21, 201368th International Symposium on Molecular Spectroscopy
HCO+ Integrated Intensity
• Column densities:
– Range: Ntot ~ 1.4 × 1011 – 2.4 × 1012 cm-2
– Average: Ntot ~ 4 × 1011 cm-2
– Average f(HCO+/H2) ~ 5.3 × 10-8 cm-2
June 21, 201368th International Symposium on Molecular Spectroscopy
Comparing Atomic and Molecular emission
H2 Optical
HCO+ CO
June 21, 201368th International Symposium on Molecular Spectroscopy
Velocity Partitions
CO (Young et al 1999) HCO+ (J=1-0)
June 21, 201368th International Symposium on Molecular Spectroscopy
Velocity vs. Position Angle
Young et al 1999
CO
June 21, 201368th International Symposium on Molecular Spectroscopy
Velocity vs. Position AngleHCO+
June 21, 201368th International Symposium on Molecular Spectroscopy
Velocity vs. Position AngleHCO+
June 21, 201368th International Symposium on Molecular Spectroscopy
Red/Blue shift separated plots
Red shift Blue shift
June 21, 201368th International Symposium on Molecular Spectroscopy
H2 Overlays
-35 km/s -11 km/s
O’Dell ModelSpeck, A. 2002
June 21, 201368th International Symposium on Molecular Spectroscopy
3D Structure
June 21, 201368th International Symposium on Molecular Spectroscopy
Summary• The HCO+ emission is coincident with the CO
emission, indicating that dense gas exists throughout the Helix
• Molecular distribution corresponds with atomic emission, indicating that molecular material is ubiquitous.
• The model for the structure of the Helix has been improved.
June 21, 201368th International Symposium on Molecular Spectroscopy
Acknowledgements
FundingNASANSF
Ziurys GroupMatt Bucchino, Debbie Schmidt, DeWayne Halfen, Lucy Ziurys, Julie Anderson, Jessica Edwards, Jie Min, Gilles
Adande, and Debbie Schmidt