Primordial Disks: From Protostar to Protoplanet

1. Primordial Disks: From Protostar to Protoplanet Jon E. Bjorkman Ritter Observatory

2. Cloud Cores

3. Bok Globule: Isolated Cloud Core

4. Theorist’s Cloud Core

5. Star Formation • Within Cloud Cores • gravity overcomes gas pressure • gas must be cold • cores collapse • Free-fall • Inside out (Shu 1977) • Form protostars • rotation • Cloud flattens into disk • material falls on disk • protostar • accretes material from disk

6. Rotating Infall • Streamlines follow ballistic trajectories • Ulrich (1976); Cassen & Moosman; Terebey, Shu, & Cassen (1984) Keto

7. Accretion with Rotation • Accretion termination shock above/below disk surface • Material added at centrifugal radius (orbital periastron) • Centrifugal radius grows with time Keto

8. Young Stellar Objects

9. Circumstellar Disks

10. Disk Winds • Magneto-Centrifugal • Blandford & Payne (1982) • Pudritz & Norman (1983) • Magnetospheric • X Wind (Shu et al. 1994) Matt 2005

11. T Tauri SED • IR Excess • Starlight reprocessed by disk (passively irradiated disk) • Ldisk ~ 1/4 Lstar • Shape determined by temperature vs radius • UV excess • Disk-Star boundary layer / accretion shock • Causes “veiling” of spectral lines Adams, Lada, & Shu 1987

12. SED Classification • Class 0-III • Adams, Lada & Shu 1987 • Class 0: • Mostly sub-mm emission • Deeply embedded protostars • Class I: • Rising SEDs from 2 to 100 mm • Protostars still accreting from infalling envelope • Class II (Classical T Tauri): • Falling IR SEDs • Stars surrounded by disks • Class III (Weak-lined T Tauri): • Little IR excess • Almost no circumstellar material

13. Star/Disk Formation Sequence Class 0 Class I Class II Class III Debris Disks

14. Keplerian (Orbiting) Disks • Fluid Equations • Vertical scale height (Keplerian orbit) (Hydrostatic) (Scale height)

15. Disk Temperature Adams, Lada, & Shu 88Flat Reprocessing Disk Kenyon & Hartman 87Flared Reprocessing Disk

16. Flaring Effects:Disk Temperature & SED Near IR Far IR log wavelength (micron) Kenyon & Hartmann 87

17. Viscous Accretion Disk • Sources of Viscosity • Eddy Viscosity (Shakura & Sunyaev 1977) • Magneto-Rotational Instability (Balbus & Hawley 1991) requires slight ionization • Possible dead zones in disk interior Lee, Saio, Osaki 1991

18. Viscosity in Keplerian Disks • Viscosity • Diffusion Timescale (eddy viscosity) Lynden-Bell & Pringle 1974

19. Steady State Accretion a-Disks (Keplerian orbit) (continuity eq.) (surface density) (hydrostatic) (scale height)

20. Power Law Approximations • Keplerian Accretion Disk • Flaring

21. 3-D Monte Carlo Radiation Transfer • Divide stellar luminosity into equal energy packets • Pick random starting location and direction • Transport packet to random interaction location • Randomly scatter or absorb photon packet • When photon escapes, place in observation bin (frequency and direction) REPEAT 106-109 times

22. T Tauri Model SED

23. MC Radiative Equilibrium • Sum energy absorbed by each cell • Radiative equilibrium gives temperature • When photon is absorbed, reemit at new frequency, depending on T

24. T Tauri Envelope Absorption

25. Monte Carlo Disk Temperature Whitney, Indebetouw, Bjorkman, & Wood 2004

26. Radial Temperature Structure Optically thin T ~ r-0.4 Surface Snow Line: Water Ice Methane Ice Midplane

27. Vertical Temperature Structure Dullemond

28. 3-D Temperature Effects • At large radii • outer disk is shielded by inner disk • temperatures lowered at disk mid-plane • Surface layers • Heat up to optically thin dust temperature (Chiang & Goldreich 97) • Upper layers “puff up” • Inner edge of disk • Heats up to optically thin dust temperature • Inner edge “puffed up” (relative to flat disk) • Shadows disk behind inner wall

29. Effect of Inner Wall Dullemond, Dominik, & Nata 01

30. Disk Self-Shadowing Dullemond, Dominik, & Nata 01 Dullemond 02

31. Protostar Evolutionary Sequence Spectrum Density Mid IR Image Whitney, Wood, Bjorkman, & Cohen 2003 i =80 i =30

32. Protostar Evolutionary Sequence Mid IR Image Spectrum Density i =80 i =30 Whitney, Wood, Bjorkman, & Cohen 2003

33. Disk Evolution: Decreasing Mass Wood, Lada, Bjorkman, Whitney & Wolff 2001

34. Forming Planets: Standard Model • Dust grains stick together • form rocks • Grow into planetesimals • some still survive today • Asteroids & comets • Larger planetesimals attract smaller ones (gravity) • Planetesimals accrete • form planet cores

35. Dust Processing in Disks • Gravity causes dust settling toward mid-plane • ~104 yr • Grain Growth • Grain size increases with disk age? • Ice Condensation • dust may be coated with ice • Dust Removal • Radiation Pressure • Poynting Robertson Effect • Gas Drag • Accretion onto star (or planets) • Blown away by stellar / disk wind • Evaporation (when dust gets too hot)

36. Dust Opacity • Mie Scattering Opacity • Dust has a particle size distribution

37. Dust Opacity Wood, Wolff, Bjorkman, & Whitney 2001

38. Evidence for Grain Growth ISM Dust Grains Large Dust Grains (1mm) Wood, Wolff, Bjorkman, & Whitney 2001 Bjorkman, Wood, & Whitney

39. Cotera et al. 2001 Evidence for Grain Growth Large Grain Models Small Grain Model HH30 Observations Wood et al. 1998

40. Evidence for Dust Settling • Observed scale height < thermal value • Self-Shadowed Disks? • Dust settling reduces opacity in disk surface layers • Reduced absorption in surface layers reduces disk heating • Causes outer disk collapse, producing fully self-shadowed disk

41. Holes in Protoplanetary Disks

42. Transition Disks:GM AUR SED • Inner Disk Hole Size = Jupiter’s Orbit Rice et al. 2003

43. Planet Hole-Clearing Model Rice et al. 2003

44. Planetary Gaps Kley 1999

45. Gap Structure Bjorkman et al. 05

46. Predicted Gap Images Bjorkman et al. 05

47. Predicted Gap SED Gap Only Gap + Inner Hole Varniere et al. 2004