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CO HCN

Thanks Pierre !. CO HCN. C x H y O z N w. me. Molecules in galaxies Molecules in ISM Molecules in comets. Molecules in comets Dominique Bockelée-Morvan Observatoire de Paris. 1864 first spectrum of a comet (Donati, comet Tempel C/1864 N1)

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CO HCN

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  1. Thanks Pierre ! CO HCN CxHyOzNw me Molecules in galaxies Molecules in ISM Molecules in comets

  2. Molecules in comets Dominique Bockelée-MorvanObservatoire de Paris

  3. 1864 first spectrum of a comet (Donati, comet Tempel C/1864 N1) 1868 identification of carbon and Swan bands C2 (Huggins) 1881 identification of Na, other emissions of CH, CN, C2, C3 (comet Cruls-Tebbutt 1881III) 1911 indentification of CO+ by de la Baume Pluvinel and Baldet (comet Morehouse 1908III) 1941 idendification of OH (comet Cunningham 1941I)

  4. De la Baume and Baldet (1911) C2 CO+ CN

  5. Hunt for molecules in comets(spectroscopy) • Visible and UV windows: essentially radicals and ions • exceptions : CO and S2 • tentative detection of phenanthene and pyrene in 1P/Halley • IR 2-5 mm window : fundamental bands of vibration • hot bands of water (e.g., n3-n2) • emission process : fluorescence • radio window (cm to submm): privileged tool cold atmospheres

  6. A typical optical/near-IR comet spectrum 109P/Swift-Tuttle Feldman et al. (2005)

  7. UV cometary spectra HST spectra of C/1996 B2 (Hyakutake) FUSE spectrum of C/2001 A2 (LINEAR) Feldman et al. (2002) Weaver et al. (1998)

  8. Possible idendification of phenanthrene C14H10 TKS/Vega @450 km 1P/Halley Q/Q(H2O) = 1.5x10-3 Comparaison with laser-induced fluorescence spectra /jet-cooled conditions Moreels et al. A&A 282, 643 • Possible identification of pyrene C16H10 : C16H10 / C14H10 = 0.04 • (Clairemidi et al. PSS 52, 761, 2004) • PAHs, if present, are released from grains (Joblin et al. 1997 PSS 45)

  9. Hunt for molecules in comets(spectroscopy) • Visible and UV windows: essentially radicals and ions • exceptions : CO and S2 • tentative detection of phenanthene and pyrene in 1P/Halley • IR 2-5 mm window : fundamental bands of vibration • hot bands of water (e.g., n3-n2) • emission process : fluorescence • radio window (cm to submm): privileged tool cold atmospheres

  10. IR spectroscopy IKS/VEGA Combes et al. (1986) Simple species : H2O, CO, CO2, H2CO, CH3OH 3.3-3.5 mm band : CH-bearing species in gas phase unidentified compounds at 3.42mm 3.28mm band: PAHs ? PAHs bands at higher wavelengths not seen in Hale-Bopp ISO spectra

  11. IR spectroscopy High spectral resolution ro-vibrational lines of CH4, C2H2, C2H6 CH3OH, HCN Unidentified lines need for detailed ro-vibrational structure and strength of CH3OH bands in 3 mm region + other organic species C/1999 H1 (Lee) Keck/NIRSPEC Mumma et al. (2001)

  12. Hunt for molecules in comets(spectroscopy) • Visible and UV windows: essentially radicals and ions • exceptions : CO and S2 • tentative detection of phenanthene and pyrene in 1P/Halley • IR 2-5 mm window : fundamental bands of vibration • hot bands of water (e.g., n3-n2) • emission process : fluorescence • radio window (cm to submm): privileged tool cold atmospheres

  13. Radio spectroscopy • OH 18cm lines (1973, comet Kohoutek, Nançay) • HCN 89 GHz (1985, comet Halley, IRAM 30-m) • 19 molecules (not including isotopes, radicals, ions) now detected • many first identifications in comets Hyakutake and Hale-Bopp (in Hale Bopp: 10% of the 85-375 GHz window with IRAM 30m, PdBi and CSO) • Isotopes: HDO, DCN, H13CN, HC15N, C34S, H234S • Radicals and ions: NS, CS, SO, CN, H3O+ ,CO+

  14. Historical radio spectra of comets First OH 18 cm detection (Nançay) Comet Kohoutek, Biraud et al. (1974) HCN J(1-0) detection (IRAM 30-m) Comet Halley, Despois et al. (1986)

  15. New molecules in Hale-Bopp 230.578 GHz Crovisier et al. 2004 A&A 418, L35, 2004 Ethylene glycol HOCH2CH2OH 11 lines identified in 2003 when frequencies available in Cologne database Bockelée-Morvan et al. A&A 353, 1101, 2000

  16. H2O Odin observations H2O, H218O and NH3 C/2001 Q4 (NEAT) H218O NH3 (cf N. Biver talk, tomorrow)

  17. Evidence for chemical diversity Diversity among Oort cloud comets No systematic differences between Oort cloud and « Kuiper belt » comets Crovisier 2005

  18. Upper limits for complex species Crovisier et al. A&A 418, 1141,2004

  19. Molecular complexity • abundancesm when complexity k • C2H5OH/CH3OH <1/25 • cyanopolyynes • but CH4 ~ C2H2 ~ C2H6 • reduced alcohols wrt aldehydes CH3OH > H2CO OHCH2CH2OH > CH2OHCHO Grain surface reactions ? Crovisier et al. A&A 418, 1141,2004

  20. Deuterium in comets In H2O: D/H = 3 10-4 In HCN: D/H = 2.3 10-3 Atomic D detected (HST) In CH3OH, H2CO, NH3, CH4: upper limits of 10-2 to a few 10-2 C/1996B2 Hyakutake CSO Bockelée-Morvan et al. (1998) JCMT Meier et al. (1998)

  21. Isotopic ratios

  22. Ortho-para ratios Table from Kawakita et al. 2004, ApJ601, 1152 Recent results C/2001 Q4 (NEAT) methane Tspin = 33±3 K Kawakita et al. 2005, ApJ623, L49 C/1999 S4 (LINEAR) water Tspin > 30 K Dello Russo et al. 2005, ApJ621, 537 C/1999 H1 (Lee) water Tspin ≈ 30 K idem C/2001 A2 (LINEAR) water Tspin = 23±4 K idem Why are all these temperatures similar? What is their signification?

  23. What new from Deep Impact ? A’Hearn et al. 2005 Sciencexpress Deep Impact spectra : large increase in the amount of organics compared to water • 9P/Tempel 1, 4 July 4 2005 • 4.9 x 7.6 km dark nucleus with low thermal inertia, low density, negligible strength • smooth and rough terrains, natural impact craters • DI impact: fine dust ejected, no dramatic increase in gas production (see Biver talk) Keller et al. 2005 Sciencexpress

  24. Strong increase in silicate emission after impact • Numerous bands reported : Al2O3, PAHs, smectite clay, carbonates ….

  25. PUB Deep Impact : les premiers resultats Olivier Groussin Observatoire de Meudon Lundi 7 Novembre 11H

  26. Open questions in comet chemistry HNC@PdBi • a lot of lines still unidentified • some radicals remain orphans : e.g. C3, NS • origin of HNC : coma or nucleus product • origin of CN ? • nature of distributed sources of H2CO and CO • nature of dust organics ? • How abundances in the coma are related to abundances in the nucleus ? (chemical differenciation in the nucleus) • degree of compositional heterogeneity in comet nuclei

  27. What the composition tells us about the origin of comet material? • molecular composition present analogies with composition of star forming regions and interstellar ices • D/H ratios kept interstellar signatures • unequilibrated ortho/para ratios low-T formation (grain surface, ion-molecule processes) • highly processed material is present however (cristalline silicates) mixing with nebular products Chemical diversity in comets : how to explain it ?

  28. Future prospects • current instrumentation : bright comets needed studies are focussing on chemical diversity/spatial distribution • ALMA : factor 10 increase in sensitivity large uv-coverage, instantaneous maps • Herschel Observatory: water, D/H ratio, bending modes of PAHs ? • Space missions : Deep impact, Rosetta

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