1 / 32

L 6: Circumstellar Disks

L 6: Circumstellar Disks. Background image: HH 30 JHK HST-NICMOS, courtesy Padgett et al. 1999, AJ 117, 1490. L 6: Circumstellar Disks. Recent reviews include: Protostars & Planets IV, Mannings, Boss & Russell (eds.) 12 Articles on Disks

maitland
Download Presentation

L 6: Circumstellar Disks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. L 6: Circumstellar Disks Background image: HH 30 JHK HST-NICMOS, courtesy Padgett et al. 1999, AJ 117, 1490 L6 - Stellar Evolution II: August-September, 2004

  2. L 6: Circumstellar Disks Recent reviews include: Protostars & Planets IV, Mannings, Boss & Russell (eds.) 12 Articles on Disks 5 Articles on Outflows Zuckerman, ARAA 2001, 39: 549 Zuckerman & Song (?), ARAA 2004, in press L6 - Stellar Evolution II: August-September, 2004

  3. L 6: Circumstellar Disks and Outflows L6 - Stellar Evolution II: August-September, 2004

  4. Flattened structures - Disks Inevitable consequence of star formation Rotation Magnetic Fields L6 - Stellar Evolution II: August-September, 2004

  5. Flattened structures - Disks Inevitable consequence of star formation Rotation I. Kant 1755 Allgemeine Naturgeschichte und Theorie des Himmels P.S. Laplace 1796, 1799 Exposition du systeme du monde Mechanique celeste Planetary System Formation ...another lecture – another time... L6 - Stellar Evolution II: August-September, 2004

  6. Mass Loss - Outflows see review article Inevitable consequence of star formation Angular Momentum Loss - Redistribution The race between mass accretion & mass loss processses L6 - Stellar Evolution II: August-September, 2004

  7. Lynden-Bell & Pringle 1974, MNRAS 168, 603: Keplerian Disk Differential Rotation + Viscosity Mass Transport Inwards Angular Momentum Transport Outwards See also Gösta Gahm’s lecture L6 - Stellar Evolution II: August-September, 2004

  8. `standard model´: e.g., Frank, King & Raine Accretion Power in Astrophysics self-consistent structure of steady, optically thick a-disk blackbody radiation and thin disk approximation When / Where valid ? L6 - Stellar Evolution II: August-September, 2004

  9. Example: Lin & Papaloizou opacities (1985 PP II) Icy grains H- Molecules bound-free free-free (Cox-Stuart-Alexander) L6 - Stellar Evolution II: August-September, 2004

  10. Grain Opacities Beckwith et al. 2000, PP IV L6 - Stellar Evolution II: August-September, 2004

  11. `standard model´: e.g., Frank, King & Raine Accretion Power in Astrophysics self-consistent structure of steady, optically thick a-disk L6 - Stellar Evolution II: August-September, 2004

  12. 40 observed SEDs of T Tauri Stars & `mean model´ of star+disk HABE Disk Structure: Dullemond & Dominik 2004 includes vertical Temperature distribution D´Alessio et al. 1999 L6 - Stellar Evolution II: August-September, 2004

  13. Gas Disks – Structure Models Steady Disks around Single Stars Boundary Conditions Rin : boundary layer, magnetosphere? Rout: ? , interstellar turbulence? Viscosity MHD/rotation (Hawley & Balbus 1995) Opacity k = k(r, T, …, XYZ, ..., z0,..., cn ...) Models Adams & Shu 1986 (flat) [examples] Kenyon & Hartmann 1987 (flared) Malbet & Bertout 1991 (vertical structure) D´Allessio et al. 1998,... 2003 Aikawa & Herbst 1998 (chemistry) Nomura 2002 (2D) Wolf 2003 (3D) L6 - Stellar Evolution II: August-September, 2004

  14. Observations of Keplerian Disks JE Keeler 1895 ApJ 1: 416 The Rings of Saturn spectrum image Courtesy Brandeker, Liseau & Ilyn 2002 L6 - Stellar Evolution II: August-September, 2004

  15. 2 Categories of Disks T Tauri Disks: around young stars (0.1 - 10 Myr) of half a solar mass (0.1 - 1 Msun) at 150 pc distance (50 - 450 pc) in and/or near molecular clouds Accretion Disks Debris Disks: around young ms-stars (10 - 400 Myr) of about a solar mass (1 - 2 Msun) at 20 pc distance (3 - 70 pc) in the general field Vega-excess stellar disks gas rich gas poor L6 - Stellar Evolution II: August-September, 2004

  16. Frequency of Disks High Rate of occurence around young stars NGC 2024 86% Trapezium cluster 80% IC 348 65% Haisch et al. 2001 and around BDs in Trapezium cluster 65% Muench et al. 2001 see also G. Gahm’s lecture L6 - Stellar Evolution II: August-September, 2004

  17. Fridlund et al. 2002 for One Object Gas Disks - Sizes • Size scale (AU) Tracer (mode)* Reference • 20000 CS (1- 0) (S) Kaifu et al. 1984 • 5000 - 10000 13CO (1- 0) (S) Fridlund et al. 1989 • 1400 C18O (1- 0) (I) Sargent et al. 1988 • <500 1.4 mm (I) Woody et al. 1989 • 45 + 1600 mm, cm (I) Keene & Masson 1990 • 200 0.8 mm (I) Lay et al. 1994 • 7000 H13CO+ (1- 0) (S) Mizuno et al. 1994 • 5000 0.7 - 1 mm (S) Ladd et al. 1995 • 4000 - 6000 C18, 17O (2- 1) (S) Fuller et al. 1995 • 1200 13CO (1- 0) (I) Ohashi et al. 1996 • 4000 H13CO+ (1- 0) (I) Saito et al. 1996 • 5000 H12, 13CO+ (1- 0) (S, I) Hogerheijde et al.1997, 98 • 2500 C18O+ (1- 0) (I) Momose et al. 1998 *S=single dish, I=Interferometer Size depends on frequency/mode of observation L6 - Stellar Evolution II: August-September, 2004

  18. generally Gas Disks - Sizes T Tauri/HABE disks 50 - 100 AU Dust: mm-continuum interferometry 100 - 300 AU Dust: scattered stellar light 300 AU Gas: CO lines (evidence for Kepler rotation) Silhouettte disks (``proplyds´´) up to 1000 AU Dust: scattered stellar light L6 - Stellar Evolution II: August-September, 2004

  19. Gas Disks - Masses H2 Gas Directly CO and Dust L6 - Stellar Evolution II: August-September, 2004

  20. Gas Disks - Masses ? Why ? Lower limit: 0.001 to 1 MSun(based on mm / submm continuum) gas+dust dust How good are these numbers ? Do we understand disks ? Solar Minimum Mass Nebula = 0.002 MSun L6 - Stellar Evolution II: August-September, 2004

  21. Gas Disks - Make up gas disks consist of gas and dust what components? what proportions? L6 - Stellar Evolution II: August-September, 2004

  22. 2 T Tauri Disks - Make up 13CO (1)* HCO+ (5) HCN (5) CO (200) HCO+ (200) HCN (200) *(N) =depletion factor van Zadelhoff 2002 LkCa 15 TW Hya L6 - Stellar Evolution II: August-September, 2004

  23. 2 T Tauri Disks - Chemistry Molecular abundances (rel. H2) Species LkCa 15 TW Hya CO 3.4 ( - 7) 5.7 ( - 8) HCO+ 5.6 (-12) 2.2 (-11) H13CO+< 2.6(-12) 3.6 (-13) DCO+ …. 7.8 (-13) CN 2.4 (-10) 1.2 (-10) HCN 3.1 (-11) 1.6 (-11) H13CN …. < 8.4(-13) HNC …. < 2.6(-12) DCN …. < 7.1(-14) CS 8.5 (-11) …. H2CO 4.1 (-11) < 7.1(-13) CH3OH < 3.7(-10)< 1.9(-11) N2H+< 2.3(-11)< 1.8(-11) H2D+< 1.5(-11)< 7.8(-12) Thi 2002 L6 - Stellar Evolution II: August-September, 2004

  24. Gas Disks - Evolution • Time scales (viscous accretion disk) • tdyn ~ attherm ~ a (H/R)2tvisc • tdyn ~ 1/WKepler • ~ 10-3 - 10-2 H/R << 1 if T ~ R-1/2 , tvisc ~R tvisc ~ 105 yr (a/0.01)-1 (R/10 AU) L6 - Stellar Evolution II: August-September, 2004

  25. Gas Disks - Evolution Disk dispersal and disk lifetimes SE = Stellar Encounter (tidal stripping) WS = Stellar wind stripping evap E = photoevaporation external star evap c = photoevaporation central star All for Trapezium conditions Physical Mechanisms Hollenbach et al. 2000 PPIV L6 - Stellar Evolution II: August-September, 2004

  26. Gas (T Tauri) Disks - Evolution Disk dispersal and disk lifetimes Average Error Bar Mass accretion evolution Calvet et al. 2000 PPIV L6 - Stellar Evolution II: August-September, 2004

  27. Gas Disks to Debris Disks – Evolution ? How ? fdust = DLIR/Lvs stellar age See also lecture by G. Gahm (F)IR - excess Stellar luminosity (bolometric) L6 - Stellar Evolution II: August-September, 2004

  28. Gas Disks to Debris Disks – Evolution ? Clusters Individual stars (= 1 zodi) Spangler et al. 2001 L6 - Stellar Evolution II: August-September, 2004

  29. Debris Disks - Properties debris (collision products) or particulate (gas free) percentage of Main Sequence stars (15%?) (observationally) biased towards Spectral Type A for (detectable) ages <400 Myr Habing et al. 1999, 2001 disk sizes 100 to 2000 AU disk masses >1 to 100 MMoon(small grains) Pre-IRAS Solar system Zodi US Navy Chaplain G. Jones 1855 AJ 4, 94 Vega Blackwell et al. 1983 L6 - Stellar Evolution II: August-September, 2004

  30. http://www.hep.upenn.edu/~davidk/bpic.html L6 - Stellar Evolution II: August-September, 2004

  31. How much Gas in Dusty Debris Disks ? Disk evolution hypothesis: gas rich to gas poor Census of material (mgas/mdust): planet formation planet formation: enough gas for GPs ? planet formation: time scales? planet formation: seeds of Life ? See review L6 - Stellar Evolution II: August-September, 2004

  32. L 6: conclusions • circumstellar disks are a consequence of star • formation • disks and bipolar outflows/jets are connected • disks form potentially planetray systems • L 6: open questions • what are the physics of disks and their outflows ? • how do disks evolve ? • what fraction forms planetary systems ? • when and how ? L6 - Stellar Evolution II: August-September, 2004

More Related