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Molecular Hydrogen Emission from Protoplanetary Disks

Modeling the structure, chemistry and appearance of protoplanetary disks. Molecular Hydrogen Emission from Protoplanetary Disks. Hideko Nomura (Kobe Univ.), Tom Millar (UMIST). §1 Introduction. Obs. of Protoplanetary Disks. SED of TTS + disk. Disk. Central Star. Star. Disk.

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Molecular Hydrogen Emission from Protoplanetary Disks

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  1. Modeling the structure, chemistry and appearance of protoplanetary disks Molecular Hydrogen Emission from Protoplanetary Disks Hideko Nomura (Kobe Univ.), Tom Millar (UMIST)

  2. §1 Introduction

  3. Obs. of Protoplanetary Disks SED of TTS + disk Disk Central Star Star Disk (Chiang & Goldreich 1997) 106yr 107yr WTTS CTTS (Andre et al. 1994)

  4. Observations of H2 Line Emission MIR GG Tau, GO Tau, LkCa 15 J=2-0, J=3-1 by ISO (Thi et al. 2001) NIR GG Tau, TW Hya, LkCa 15, DoAr25 (v,J)=(1,3)-(0,1) by NOAO (Bary et al. 2003) UV TW Hya 146 Lyman-band H2 lines by HST, FUSE (Herczeg et al. 2002) etc.

  5. H2 Transition Lines UV pumping UV fluorescent line emission Infrared quandrapolar cascades (Shull & Beckwith 1982) continuous fluorescence (UV) UV pumping H+H collisional excitation, de-excitation Collisional process level populations v=0 radiative cascade (IR) UV radiation field Temperature profile

  6. Irradiation from Central Star Disk Central Star (Chiang & Goldreich 1997) Irradiationfrom central star H2 level transitionsviaUV pumping Heat gas & dust in disks Radiative transfer process Global physical disk structure (gas & dust temperature, and density profiles) H2 level populations&line emission

  7. §2 Disk Model

  8. Gas Density & Temperature z x ★ ・ Macc=10-8Ms/yr (=const.) Hydrostatic equilibrium in z-direction cs2=2kT/mmp W(x)=1.4x10-7 s-1(x/1AU)-3/2 (M*=0.5 Ms ) Thermal equilibrium(Gpe+Lgr-Lline=0) Gpe :Grain photoelectric heating by FUV Lline :Cooling by OI, CII & CO line excitation Lgr :Energy exchange by collisions between gas and dust particles

  9. Dust Temperature Local radiative equi. (abs.=reemission) • Heating sources: • viscous heating at equatorial plane • (B) radiation from central star 2D radiative transfer equation Short characteristic method in spherical coordinate (Dullemond & Turoulla 2000)

  10. UV Radiation from Central Star UV excess Stellar blackbody (T*=4000K) +Thermal bremsstrahlung (Tbr=2.5 x 104K) TW Hya (Costa et al. 2000)

  11. Resulting Temperature Profile R=0.1AU 1AU 10AU Disk surface heated up byphotoelectric heating Midplane & Outer disk (without UV excess)gas temp. = dust temp. with UV excess without UV excess R=0.1AU 1AU 10AU

  12. §3 H2 Level Populations

  13. H2 Level Populations blm UV bml UV Statistical Equilibrium u, B1Su+ , C1Pu H+H H+H Rdiss,l m, X1Sg+ Em>El Aml Clm Cml Rform,l l, X1Sg+

  14. Resulting Level Populations R=0.1AU R=0.1AU 10AU v=0 v=1 v=2 v=3 v=4 10AU with UV excess without UV excess v=0 v=1 v=2 v=3 v=4 with UV excess or Inner disk (hot) : LTE collisional process,nupper: large Outer diskwithout UV excess (cold): non-LTE UV pump. & cascade,nupper: small

  15. §4 Resulting H2 Line Emission with UV excess:Tgas: nu: Iul: Observer Iul with UV excess:UV: nu: Iul: Sul IR [erg/cm-2/s] v=1-0 S(1) (@2.12mm) Obs.(Bary et al.’03) with UVewithout UVe (1.0 - 15) x 10-15 9.3 x 10-153.3 x 10-18 UV [erg/cm-2/s] e.g., v=1-7 R(3) (@1489.6A) Obs.(Herczeg with with UVewithout et al.’02) UVe + Lya UVe 4.8 x 10-14 1.4 x 10-141.3 x 10-16 4.0 x 10-22

  16. §5 Discussion

  17. Dustless Disk Model Conserv. of dust mass & dust size growth amount of small dust Planet formation Dustless disk model SED Dustless disk : no infrared excess

  18. Resulting Temperature Profile R=0.1AU 1AU 10AU with UV excess Dusty Dustless R=0.1AU 1AU 10AU Dustless (ndust/ngas: small) grainphotoelectric heating Tgas

  19. Resulting Level Populations Outer region of dustless disk(cold): non-LTE UV pump. & cascade nupper: large UV radiation fields dust absorption with UV excess Dusty Dustless R=0.1AU R=0.1AU 10AU v=0 v=1 v=0 v=2 v=3 v=1 v=4 v=2 v=3 v=4 10AU

  20. Resulting H2 Line Emission [erg/cm-2/s] v=1-0 S(1) (@2.12mm): Obs.(Bary et al.’03) DustyDustless (1.0 - 15) x 10-15 9.3 x 10-156.5 x 10-16 S(0) (@28.2mm), S(1) (@17.0mm): Obs.(Thi et al.’01) DustyDustless S(0)(2.5 – 5.7) x 10-14 4.2 x 10-179.3 x 10-17 S(1)(2.8 – 8.1) x 10-14 8.5 x 10-165.0 x 10-16 UV (@900A-2900A) Obs.(Herczeg et al.’02) DustyDustless (1.2 - 73) x 10-15 3.8 x 10-15 1.2 x 10-14 Obs. possibility to detect H2 emission from dustless disks in NIR & UV

  21. §6 Summary UV excess+Radiative transfer process Gas & dust temperature, density profiles Gas temperature@disk surface:~2,000K Grain photoelectric heating H2 level populations : LTE,nupper: large Strong NIR H2 lines : consistent with obs. collisional excitation (hot gas) Strong UV H2 lines : consistent with obs. pumping by Lya emission H2 emission from dustless disks

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