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Last review on disk chemistry in Protostars and Planets : Prinn (1993) Kinetic Inhibition model - (thermo-)chemical timescale vs (radial) mixing timescale - constraints and goals … composition of solar system materials. Background. Since then….

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  1. Last review on disk chemistry in Protostars and Planets: Prinn (1993) Kinetic Inhibition model - (thermo-)chemical timescale vs (radial) mixing timescale - constraints and goals … composition of solar system materials Background Since then… • Spectroscopic observation of disks in mm, sub-mm, infrared • e.g. Dutrey et al., Najita et al. • Detailed models of disk structure • e.g. Dullemond et al.

  2. Outline • General Theoretical Picture - disk structure - key ingredients: UV, X-ray, Cosmic-ray • Observations - mm & sub-mm - infrared • Chemical-Physical Likns - thermal structure - grain evolution - ionization degree - mixing • Deuterium Chemistry and Comets • Future

  3. General Theoretical Picture three-layer model (i)photon-dominant layer UV & X-ray irradiation low density (nH< 105cm-3) high temperature (T > several 10 K) vertical distribution @ r ~300 AU -4 -6 log n(i)/nH -8 -10 -12 0 100 200 300 400 height from midplane [AU] Aikawa & Herbst (1999) Willacy & Langer (2000) Aikawa et al. (2002) van Zadelhoff et al. (2003)

  4. General Theoretical Picture three-layer model (i)photon-dominant layer UV & X-ray irradiation low density (nH< 105cm-3) high temperature (T > several 10 K) (ii) warm molecular layer high density (nH> 105cm-3) moderate temperature (T > 20 K) vertical distribution @ r ~300 AU -4 -6 log n(i)/nH -8 -10 -12 0 100 200 300 400 height from midplane [AU] Aikawa & Herbst (1999) Willacy & Langer (2000) Aikawa et al. (2002) van Zadelhoff et al. (2003)

  5. General Theoretical Picture three-layer model (i)photon-dominant layer UV & X-ray irradiation low density (nH< 105cm-3) high temperature (T > several 10 K) (ii) warm molecular layer high density (nH> 105cm-3) moderate temperature (T > 20 K) (iii) midplane freeze-out layer very high density (nH> 107cm-3) low temperature (T < 20 K) vertical distribution @ r ~300 AU -4 -6 log n(i)/nH -8 -10 -12 0 100 200 300 400 height from midplane [AU] cf. Observation (Dutrey et al. 1997) : - high CN/HCN ratio - low abundance of gaseous molecules Aikawa & Herbst (1999) Willacy & Langer (2000) Aikawa et al. (2002) van Zadelhoff et al. (2003)

  6. General Theoretical Picture three-layer model (i)photon-dominant layer UV & X-ray irradiation low density (nH< 105cm-3) high temperature (T > several 10 K) (ii) warm molecular layer high density (nH> 105cm-3) moderate temperature (T > 20 K) (iii) midplane freeze-out layer very high density (nH> 107cm-3) low temperature (T < 20 K) (iv) inside snow line (r < 10 AU) thermal desorption “hot core” like chemistry (Najita et al. talk; Markwick et al. 2002; Ilgner et al. 2004) vertical distribution @ r ~300 AU -4 -6 log n(i)/nH -8 -10 -12 0 100 200 300 400 height from midplane [AU] Aikawa & Herbst (1999) Willacy & Langer (2000) Aikawa et al. (2002) van Zadelhoff et al. (2003)

  7. Key ingredients • X-rays from central star • excite molecules (Tine et al. 1997) • ionization (Glassgold et al. 1997) • induce UV photons (Bergin et al. 2005) • non-thermal desorption (Najita et al. 2001) enhance HCN, CN, HCO+ (Aikawa & Herbst 1999; 2001;Markwick et al. 2002) r=700AU 10-15 Lx=1031 erg/s 1030 erg/s ionization rate [s-1] F (erg cm-2 s-1 Å-1) X-ray induced UV ? 10-16 1029 erg/s 1028 erg/s height from midplane [AU] wavelength (Å)

  8. Key ingredients • X-rays from central star • excite molecules (Tine et al. 1997) • ionization (Glassgold et al. 1997) • induce UV photons (Bergin et al. 2005) • non-thermal desorption (Najita et al. 2001) enhance HCN, CN, HCO+ (Aikawa & Herbst 1999; 2001;Markwick et al. 2002) local hot spot ejected molecules -5 CO X-ray desorption X-ray -7 only thermal HCN log n(i)/nH -9 CN -11 grain aggregate -13 0 20 40 60 80 height from midplane [AU]

  9. Key ingredients • Cosmic-rays • ionization … driving force for chemistry in molecular clouds • - attenuation length 96 g cm-2 (Umebayashi & Nakano 1981) • - scattered by magnetic field ?? • non-thermal desorption

  10. Key ingredients • UVfrom central star and interstellar field • photo-dissociation and ionization • - require 2D radiation transfer with scattering (van Zadelhoff et al. 2003) • - contribution of Lya line (Bergin et al. 2003; 2006) • photo-desorption -4 1+1D interstellar UV -6 stellar UV log n(i)/nH -8 -10 -12 2D scatter -6 scattering -8 log n(i)/nH -10 -12 height from midplane [AU]

  11. Ly  0 C III -2 Log10 F (at 100 AU) (erg cm-2 s-1 Å-1) -4 1250 1200 wavelength (Å) Key ingredients • UVfrom central star and interstellar field • photo-dissociation and ionization • - require 2D radiation transfer with scattering (van Zadelhoff et al. 2003) • - contribution of Lya line (Bergin et al. 2003; 2006) • photo-desorption -4 CO -5 strong La -6 log n(i)/nH -7 H2O -8 weak La -9 height from midplane [AU]

  12. Sigle Dish Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice water, CO, CO2, NH4+ Dutrey et al. (1997), IRAM 30m - trace r > several 10 AU - high CN/HCN ratio - low abundance of gaseous molecules

  13. Interferometer -less dilution - imaging Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice water, CO, CO2, NH4+ NT(CS) = 1013-1014 cm-2 Upper limits only for H2S,SO,SO2 CS dominant

  14. Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice water, CO, CO2, NH4+ Lahuis et al. (2006), Spitzer - T > 300 K - r << 100 AU - n(i)/nH=10-6-10-5 cf. Markwick et al. (2001)

  15. Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI double-peak  disk rotation Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice water, CO, CO2, NH4+ Acke et al. (2005) - traces disk surface at r < 1AU ~

  16. Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI LkHa330 PHA PHA Silicate Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice water, CO, CO2, NH4+ Geers et al. (2006) - r = 10-100 AU - in 50% of Herbig Ae 15 % of T Tauri stars  long timescale for settling and growth

  17. Observation Detected species: Gas-Phase radio: - neutral: H2, CO, CN, HCN, CS, H2CO, C2H, - ion: HCO+, N2H+, H2D+, - deuterated: HDO, H2D+, DCN mid-IR: C2H2, HCN, CO2 NIR: CO, H2O (Najita et al.) Optical: OI Pontoppidan et al. (2005) Solid amorphous & crystalline silicates (Wooden et al.) PAH Ice H2O, CO, CO2, NH4+ edge-on disk - ice absorption bands against scattered light and warm dust emission - upto 50 % of CO2 and H2O are in disk

  18. Chemical-Physical Links: gas thermal structure Tgas and Tdust are not necessarily equal. heating cooling dust radiation from thermal radiation star or upper layer gas UV (photo-electric) lines (C+, CI, OI …) gas-dust collision gas-dust collision (Dullemond et al.; Inga & Dullemond 2004; Junkheid et al. 2004) • energy balance and chemistry have be solved simultaneously • density distribution is determined by Tgas  Self-consistent calc of Tgas, Tdust, and density distribution (Nomura & Millar 2005) • Tgas > Tdust at the surface layer  extended disk “atmosphere” • no hot finger (?)

  19. > ~ ISM dust amax=1mm D’Alessio et al. (2001) Chemical-Physical Links: Grain Growth • Grains must coagulate & sediment to make planets • calculation of coagulation equation • (Weidenschiling@PPII, Dullemond & Dominik 2005, Tanaka et al. 2005) • SEDs and disk images are better reproduced with amax 1 mm • (Miyake & Nakagawa 1995; D’Alessio et al. 2001; Chiang et al. 2001) •  dust opacity decreases at UV wavelength

  20. Chemical-Physical Links: Grain Growth • As dust grows… • UV penetrates deeper into the disk •  T @intermediate height increases • Photoelectric heating becomes less efficient •  T @disk surface decreases •  disk is less flared-up • Molecular layer is pushed down to lower heights Junkheid et al. (2004) Aikawa & Nomura (2006)

  21. Chemical-Physical Links: ion fraction • Angular momentum transport by Magneto-Rotational Instability • - magnetic field decouples if ionization degree (xe) is too low • - accretion and turbulence may be active only on disk surface Gammie (1996)

  22. Chemical-Physical Links: ion fraction • Angular momentum transport by Magneto-Rotational Instability • - magnetic field decouples if ionization degree (xe) is too low • - accretion and turbulence may be active only on disk surface photoionization of H: xe > 104 photoionization of C: xe~ 104 Cosmic-ray and X-ray ionization: xe~ 10-11 - 10-6 HCO+, H3+ Cosmic-ray and Radionucleide: r < 3AU 3 AU < r < 60 AU r > 60 AU xe< 10-12 xe~ 10-12 xe> 10-11 Metal+/grain HCO+/grain H3+ & D3+ (Sano et al. 2000; Semenov et al. 2004) agreement with simple chemistry ?? -> TED

  23. Chemical-Physical Links: mixing • Three must be some mixing in the disks, because… • - angular mom. transport by turbulent viscosity • - crystalline silicate in disks and comets • - refractory inclusions in meteorites • Chemistry is modified if tmix < tchem: tmix ~tvis ?(cf. Carballido et al. 2005) Stationary z-mixing Advection &r-mixing 1.0 Z/Zmax Semenov et al. (2006) in prep • Three-layer structure is preserved • because tchem is small in the surface • and midplane • Species formed on grains (ex. H2CO) • are enhanced by vertical mixing • Ionization fraction is not modified CS 0.1 NH3 H2CO electron see also Willay et al. and Ilgner et al. 10 100 R [AU]

  24. Deuterium chemistry in disks • Isotopic fractionations in comets and meteorites • D/H enrichment in low temperature • - D-H exchange reactions • H3+ + HD  H2D+ + H2 + 230K • H2D+ + CO  HCO+ + HD • H2D+ + e  H2 + D • - Further enhancement by CO depletion survival of interstellar matter ? nebula process ?

  25. Deuterium chemistry in disks Detection of deuterated species in disks ! species col [cm-2] D/H object DCO+ 3x1011 0.035 TW Hya HDO (0.064) LkCa15 8x1012 (1x10-3) DM Tau DCN (< 2x10-3) LkCa15 o-H2D+ 4x1012 DM Tau 6x1013 TW Hya H2D+ TW Hya van Dishoeck et al. (2003), Kessler et al. (2003), Caccarelli. et al. (2004; 2005), DM Tau TW Hya HDO

  26. Deuterium chemistry in disks Detection of deuterated species in disks ! species col [cm-2] D/H object DCO+ 3x1011 0.035 TW Hya HDO (0.064) LkCa15 8x1012 (1x10-3) DM Tau DCN (< 2x10-3) LkCa15 o-H2D+ 4x1012 DM Tau 6x1013 TW Hya van Dishoeck et al. (2003), Kessler et al. (2003), Caccarelli. et al. (2004; 2005), Model: - High D/H right above the midplane - Midplane is traced by H3+, H2D+, HD2+, D3+  grain size & ionization rate Ceccarelli & Dominik (2005)

  27. species col [cm-2] D/H object DCO+ 3x1011 0.035 TW Hya HDO (0.064) LkCa15 8x1012 (1x10-3) DM Tau DCN (< 2x10-3) LkCa15 o-H2D+ 4x1012 DM Tau 6x1013 TW Hya Deuterium Chemistry: Links to Comets D/H in comets HDO 3x10-4 (2x10-3) DCN 2x10-3 Comet: ice @ r= 5-30 AU cf. radio obs: gas beam size > 100 AU • D/H changes while fluid parcel migrates • towards the inner radius (Aikawa & Herbst 1999) • … mixing is not considered • D/H is determined by radial mixing (Hersant et al. 2001) • … only thermal reactions D/H model with mixing (radial & vertical) and full chemistry is highly desirable !

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