Protoplanetary Disks: An Observer’s Perpsective

1. Chunhua Qi Meredith Hughes Sean Andrews (Hubble Fellow) Andrews et al. 2008 Burrows et al. 1996 Protoplanetary Disks: An Observer’s Perpsective David J. Wilner (Harvard-Smithsonian CfA) RAL 50th, November 13, 2008

2. Circumstellar Disks Shu, Adams & Lizano, 1987 ARA&A • integral part of star/planet formation paradigm before disks spatially resolved • inevitable consequence of gravity + ang. mom. • Solar System fossil record • preponderance of circumstantial evidence • observational challenges • bulk of disk mass is cold (and dark) H2, probed by minor constituents only • Solar System scales small, difficult to image 100 AU 0.7” @ 140 pc

3. Panchromatic Systems x-ray uv optical mid/far-ir submm cm hot gas/accr. starlight warm… cool gas & dust dust dominates the opacity, gas dominates the mass Dullemond et al. 2007

4. optical shadows are beautiful but opaque  mm emission Imm  B(T)(1 - e-)d 1 - e-     where  dust emissivity Rayleigh-Jeans: B(T)  T Lmm ∫ T Md typical Md  0.01 M (wide range exists) for > 300 systems in nearby Taurus and  Oph clouds Disk Masses Andrews & Williams 2007 (cf. Beckwith et al. 1990)

5. — Adams, Shu & Lada 1988 Disk Mass Distributions S(r)~ r -p “Minimum Mass Solar Nebula” Steady Irradiated  Disk S~ r-1.5 S~ r-1.0 D’Alessio et al. 2001 Weidenschilling 1977 (also Hayashi 1981) ncsH (Shakura & Sunyaev 1973) S ~ (dM/dt)/3pn ~ (r1.5T)-1~ r-1

6. Submillimeter Array Survey flux limited sample:  Oph (125 pc) and TWA (50 pc) regions 870 microns, 0.25” resolution, surface density structure to r < 20 AU

7. 100 AU SMA Survey (12 disks so far) Oph TWA

8. Surface Density Distributions • fit resolved submm data and SED simultaneously • stellar properties • dust properties (uniform) • Dullemond RADMC code (temperature structure computed, not imposed)

9. Surface Density Distributions   r-1 densities comparable to MMSN (extrapolation) + significant mass reservoir good potential for planet formation(e.g. Inaba et al. 2003, Hubickyj et al. 2005) Andrews et al., in prep

10. Evidence for Central Holes • other two  Oph disks… diminished emission inside r ~ 20-40 AU growing sample of disks with large central holes mechanism(s)? J. Brown, Ph.D. thesis (see Pontoppidan et al. 2008) Andrews et al., in prep

11. SMA TW Hya CO 3-2 Isella et al. 2007 Spectral Line Emission • CO: most abundant gas tracer of H2(e.g. Koerner et al. 1993, Mannings et al. 1997, Dutrey et al. 1997, Simon et al. 2000, …) • low J lines collisionally excited, thermalized, optically thick (T r-0.5) • confusion with ambient cloud is often a major problem • many other (much weaker) species (e.g. Kastner et al. 1997, Dutrey et al. 1997, van Zadelhof et al. 2003, Thi et al.. 2004, …) • rich chemistry: ion-molecule, deuteration, photo-, organics • HCO+, DCO+, HCN, CN, DCN, CS, H2CO, CH3OH, … Hughes et al., in prep (Qi et al. 2004, 2006) SMA HD 163296 CO 3-2

12. Velocity Fields TW Hya SMA CO 3-2 v = 44 m/s • Keplerian rotation • v  r-0.5 • turbulence? • subsonic (if present) Hughes et al., in prep

13. Nebular Chemistry • D/H enhanced at low temps: H3+ + HD  H2D+ + H2 + E • is pristine cometary material: “interstellar” or “nebular”? • TW Hya: radial distributions of DCO+ and HCO+ • D/H ratio  from 0.01 to 0.1 from r<30 to 90 AU • in situ fractionation is important HCO+ 3-2 DCO+ 3-2 Qi et al. 2008

14. Outer Edge Complexity • power law models do not match observed extent of dust and CO emission • e.g. HD 163296: 200 AU (dust) vs. 600 AU (CO) • not limited sensitivity • outer disk dust:gas ratio? dust opacity? • accretion disk structure: exponential outer edge • reconciles dust and gas sizes with same model SMA 1.3/0.87 mm CO J=3-2 Hughes et al. 2008

15. Disk Magnetic Fields • aligned dust grains  linear polarization • models: ~2% pol. fraction 870 m (Cho & Lazarian 2007) • tentative JCMT detections: toroidal field (Tamura et al. 1999) • SMA polarimetry of HD 163296 • < 5x below model • magnetic field geometry? grain alignment? Hughes et al. in prep

16. Concluding Remarks • observed disk properties are “protoplanetary” • dust (Spectral Energy Distributions) • gas (accretion, flaring, mm lines) • sizes 10’s - 100’s AU (dust, mm lines) • masses ~ 0.01 M(mm dust) •  r -1(mm dust) • holes cleared by planets? (mm dust) • kinematics Keplerian (mm lines) • ALMA on the horizon: full operation 2013? • 10-100x sensitivity, resolution, image quality • global partnership to fund >$1B construction • disks are a Key Science Goal

17. END

18. Evidence for Central Holes • GM Aur disk: diminished opacity for R < 24 AU Hughes et al., in prep C. Espaillat Calvet et al. 2005

19. Transition Disk Models • dynamical clearing by planet • planet interacts tidally with disk, transfers angular momentum, opens gap, viscosity opposes(Papaloizou & Lin 1984, …) • photoevaporation • accretion rate drops below mass loss rate, open gap: “uv switch”(Clarke et al. 2001,…) • demographics favor planets • large masses • modest accretion rates Najita et al. 2007

20. infrared excess 50% (90%) gone by 3 (5) Myr also gas accretion timescale 1-2 Myr T-Tauri stars Lmm  ∫B(T)(1 - e-)d T <Md>  0.01 M Disk Mass and Disk Dispersal Hernandez et al. 2007 (cf. Haish et al. 2001) Andrews & Williams 2007 (cf. Beckwith et al. 1990)

21. “anemic” disk “cold” disk Disk Evolution: Multiple Paths? primordial disk debris disk B. Merin, Spitzer c2d team

22. At the Limits of ALMA simulated ALMA 900 GHz image Wolf & D’Angelo 2005 • hypothetical planet in TW Hya disk 5 AU model density distribution