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Acknowledgements

Formaldehyde Emission in C/2002 T7 (LINEAR): First Definitive Line-by-Line Detection in Comets at Infrared Wavelengths. Acknowledgements. NASA Astrobiology Program (RTOP 344-53-51) NASA Planetary Atmospheres Program (RTOP 344-33-55) NASA Planetary Astronomy Program (RTOP 344-32-98).

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Acknowledgements

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  1. Formaldehyde Emission in C/2002 T7 (LINEAR): First Definitive Line-by-Line Detection in Comets at Infrared Wavelengths

  2. Acknowledgements • NASA Astrobiology Program (RTOP 344-53-51) • NASA Planetary Atmospheres Program (RTOP 344-33-55) • NASA Planetary Astronomy Program (RTOP 344-32-98)

  3. SIGNIFICANCE OF H2CO AND OXIDIZED CARBON IN COMETS • The presence of formaldehyde and related molecules in comets may provide key information pertaining to the origin of life. • Relevance to Astrobiology • H2CO is fundamental in studies of oxidized carbon in comets. • Its likely means of production is repeated hydrogen addition to CO ice in grain mantles prior to their incorporation into the nucleus: CO ice + H -----> HCO -----> H2CO -----> CH3OH Such reactions have been confirmed in laboratory simulations (Hudson and Moore 1999 Icarus140:361; Watanabe et al. 2004 ApJ616:638). Provides a quantitative comparison for our retrieved abundances of CO, H2CO and CH3OH in comets.Our measured mixing ratios CO:H2CO:CH3OH in cometary nuclei can test the efficiency for hydrogenation of CO on ice-mantled grains. 19mar06md

  4. Hudson & Moore 1999 Icarus140:451

  5. Modeling of Cometary Formaldehyde • Line-by-line fluorescence model (Reuter et al. 1989 ApJ341:1045) • Two fundamental bands: n1 (symmetric C-H stretch) & n5 (asymmetric C-H stretch). Recent applicability to high-res spectra. • Compare predicted line intensities with those observed in our comet spectra: • Correlation analysis to constrain rotational temperature. • Excitation analysis to rigorously obtain Trot, sTrot; hence Q. We have detected H2CO (n1 Q-branch) in 7 out of 12 comets observed since 1999. The best candidate for comparison with and testing of modeled line intensities is C/2002 T7 (LINEAR). 19mar2006md

  6. Formaldehyde fluorescencemodel (n1-, n5-bands). Reuter et al. Ap. J.341:1045 (1989) 29june04md 19mar2006md

  7. CSHELL (C/T7) 20mar06md

  8. C/T7 May 5 (D-F), May 7 (G), 15-row (1 x 3 arc-sec) sums 07nov05md

  9. 05nov04md

  10. --> --> 05nov04md

  11. 05nov04md

  12. 05nov04md

  13. 05nov04md

  14. 05nov04md

  15. 05nov04md

  16. 05nov04md

  17. 05nov04md

  18. Treat each setting separately… • avoids the question of inter-calibrating settings • provides additional insights 07nov2005md

  19. Correlation Analysis: Most Probable Trot DiSanti et al. 2006 ApJ (submitted) 21mar2006md

  20. 3-s 18mar06md

  21. C/2002 T7 (LINEAR) excitation analysis, UT 2004 May 05 DiSanti et al. 2006 ApJ (submitted) 20mar2006md

  22. Correlation Analysis: Most Probable Trot DiSanti et al. 2006 ApJ (submitted) 21mar2006md

  23. A-C: C/2002 T7 (LINEAR), UT 2004 May 05, CSHELL Hudson & Moore 1999 Icarus 140:451 Hudson & Moore 1999 Icarus 140:451 Hudson & Moore 1999 Icarus 140:451 20mar2006md

  24. Volatile Carbon Mixing Ratios (H2O = 100) and CO Conversion Efficiencies (still evolving!!) 20mar2006md

  25. Conclusions • H2CO fluorescence model is validated in C/2002 T7. • H-atom addition to CO to form H2CO and CH3OH on interstellar grain ice mantles at T ~ 10 - 15 K appears plausible, based on comparison with laboratory irradiation experiments. 16sep2005md

  26. Future Directions • Finalize native source contributions (esp. CO, H2CO). • Investigate potential additional emitting species (including isotopes) in 2760 - 2800 cm-1 region. • OPR (Tspin). 20mar2006md

  27. 104 yrs 105 yrs 106 yrs 20mar2006md

  28. 104 yrs 105 yrs 106 yrs 20mar2006md

  29. NIRSPEC (C/Lee) ------------------------ CSHELL (C/T7) 20mar06md

  30. C/1999 H1 (Lee), UT 1999 Aug 21.6, NIRSPEC Q-br | CSHELL CSHELL 29june04md 16sep2005md

  31. C/1999 H1 Lee, UT 1999 August 21.6 NIRPSEC 19mar2006md

  32. Comparison of Spatial Profiles(isolation of native source contribution) 16sep2005md

  33. | | 05nov04md

  34. “Excess” Emission in C/T7 -- CH3OH n3-band 05nov04md

  35. “Excess” Emission in C/T7 -- HDCO, etc (???) NIRSPEC ------------------------ 05nov04md

  36. 100 K model (fully-resolved, Doppler-shifted by -66 km s-1) H2CO Ortho, Para states 16sep2005md

  37. Hints for the thermal equilibrium process Nuclear spin temperature [K] Crovisier (1998)

  38. H2CO@40K -KL2-order21 - July 4, 2005

  39. CH4@40K -KL2-order23 - July 4, 2005

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