Structures in illuminated, optically thick dust disks Pawel Artymowicz , Jeffrey Fung

1. Structures in illuminated, • optically thick dust disks • PawelArtymowicz, Jeffrey Fung • U of Toronto • Origin of the observed structure in disks • Disks with structure but without planets Signposts of Planets GSFC, 18 Oct. 2011

2. HD 141596

3. FEATURESin disks:(9) blobs, clumps ￭(5) streaks, feathers ￭(4) rings (axisymm) ￭(2) rings (off-centered) ￭(7) inner/outer edges ￭(5) disk gaps ￭(4) warps, uneven wall ￭(7) spirals, quasi-spirals￭(8) tails, extensions ￭(6) THEIR ORIGIN:(11) ￭ instrumental artifacts, variable PSF, noise, deconvolution etc. ￭ background/foreground obj. ￭ planets (gravity) ￭ stellar companions, flybys ￭ dust migration in gas ￭ dust blowout, avalanches ￭ episodic release of dust ￭ ISM (interstellar wind) ￭ stellar wind, magnetism ￭ collective eff. : self-gravity or the tau > 1 instability LOTS OF CONNECTIONS (~50) !

4. Weak/no PAH emission Neutral (grey) scattering from s> grains Repels ISM dust Disks = Nature, not nurture! Size spectrum of dust has lower cutoff Radiative blow-out of grains (-meteoroids, gamma meteoroids) Instabilities (in disks) Radiation pressure on dust grains in disks Dust avalanches Quasi-spiral structure Orbits of stable -meteoroids are elliptical Dust migrates, forms axisymmetric rings, gaps (in disks with gas) Limit on fIR in gas-free disks Color effects Enhanced erosion; shortened dust lifetime Short disk lifetime Age paradox

5. Structure in dusty disks Dust-gas interaction: axisym. rings (Takeuchi and Artymowicz 2001) Create large gaps! Planets and other perturbers Overinterpreted observations (noise, background objects) Optical thickness > 1 non-axisymmetric instabilities Dust avalanches, optical thickness <<1 but > ( LIR/L*. ~ 3e-3)

6. Outward Migration of Jupiter-like planet in a MMSN-like disk.

7. Outward migration type III of a Jupiter Inviscid disk with an inner clearing & peak density of 3 x MMSN Variable-resolution, adaptive grid (following the planet). Lagrangian PPM. Horizontal axis shows radius in the range (0.5-5) a Full range of azimuths on the vertical axis. Time in units of initial orbital period.

8. Dust Avalanche(Artymowicz 1997) Process powered by the energy of stellar radiation N ~ exp (optical thickness of the disk * <#debris/collision>) N = disk particle, alpha meteoroid ( < 0.5) = sub-blowout debris, beta meteoroid ( > 0.5)

9. Ratio of the infrared luminosity (IR excess radiation from dust) to the stellar luminosity; it gives the percentage of stellar flux absorbed, then re-emitted thermally the midplane optical thickness multiplication factor of debris in 1 collision (number of sub-blowout debris) Simplified avalanche equation Solution of the simplified avalanche growth equation The above example is relevant to HD141569A,a prototype transitional disk with interesting quasi-spiral structure. Conclusion: Transitional disks MUST CONTAIN GAS or face self-destruction. Beta Pic is among the most dusty, gas-poor disks, possible.

10. ISO/ISOPHOT data on dustiness vs. timeDominik, Decin, Waters, Waelkens (2003) uncorrected ages corrected ages -1.8 ISOPHOT ages, dot size ~ quality of age ISOPHOT + IRAS fd of beta Pic = maximum dustiness of disks

11. Grigorieva, Artymowicz and Thebault (A&A, 2007) Comprehensive model of dusty debris disk (3D) with full treatment of collisions and particle dynamics.

12. Main results of modeling of collisional avalanches: 1. Strongly nonaxisymmetric, growing patterns 2. Substantial, almost exponential multiplication 3. Morphology depends on the amount and distribution of gas, in particular on the presence of an outer initial disk edge

13. Structure in dusty disks Dust-gas interaction: axisym. rings (Takeuchi and Artymowicz 2001) Planets and other perturbers Overinterpreted observations (noise, background objects) Optical thickness > 1 non-axisymmetric instabilities Dust avalanches, optical thickness <<1 but > ( LIR/L*. ~ 3e-3)

14. Theory of the tau>1 instability in disks. new Ingredients of the instability: Axisymmetric disk of opaque gas or dust w/shadowing radiation pressure on gas/dust Point source of gravity Isn’t it stable?..

15. Radiation pressure on a coupled gas+dust system that has a spiral density wave with wave numbers (k,m/r), is analogous in phase and sign to the force or self-gravity. The instability is thus pseudo-gravitational in nature and can be obtained from a WKB local analysis. Forces of selfgravity Forces of radiation pressure in the inertial frame (notice their gradient!) Forces of rad. pressure relative to those on the center of the arm

16. The instability is thus pseudo-gravitational in nature and can be obtained from a WKB local analysis. effective coefficient for coupled gas+dust (this profile results from outward dust migration; Chiang & Murray-Clay 2007; Dominik & Dullemond 2011 did not consider coagulation) r

17. Step function of r or constant 2 (WKB)

18. Step function of r or constant 2 (WKB)

19. Previously just this inverse Safronov-Toomre number Now: 2 Effective Q number (selfgravity + radiation) 1 r Analogies with gravitational instability ==> similar structures (?)

20. radius Free particles casting shadows tau = 2, beta = 0.2 1.6 1 .7 0 180 deg 360 deg azimuthal angle

21. radius Free particles casting shadows tau = 4, beta = 0.2 1.6 1 .7 0 180 deg 360 deg azimuthal angle

22. radius Free particles casting shadows tau = 12, beta = 0.2 1.6 1 .7 0 180 deg 360 deg azimuthal angle

23. Beta = 0.2 De Val Borro & Artymowicz (2008, unpubl.), FLASH hydrocode

24. Beta = 0.2

25. Beta = 0.2

26. tau = 3 beta = 0.075 PPM gas disk density soundspeed c/vk= 0.05 Navier-Stokes viscosity: alpha = 0 Azimuthal angle (0-360 deg) radius 1 2 3 (2a)

27. tau = 4 beta = 0.15 PPM gas disk density soundspeed c/vk= 0.05 Navier-Stokes viscosity: alpha = 0 Azimuthal angle (0-360 deg) radius 1 2 3 (3a)

28. NOT

29. CPU=Intel 4-core nVidia GeForce graphics processors

30. nVidia CUDA = extended C-language for GPU programming up to 5 TFLOP/s using one computer Cudak1 2 TFLOP, 484 cores Cudak2 3 TFLOP , 724 cores Cudak3 5+ TFLOP, 1444 cores all: max 10+ TFLOP, 2652 cores

31. PPM hydrodynamical simulation on GPU of a gas+embedded dust disk around with effective beta = 0.15 and total optical depth tau|| =15 Please see Jeffrey Fung’s poster on linear modal analysis which confirms that irradiated disks have a wide variety of unstable modes!

32. Not only planets but also Gas + dust + radiation => non-axisymmetric features in gas-poor and gas-rich disks, & TIME VARIABILITY due to radial, azimuthal and vertical variations in them. m=1 one armed spirals, conical sectors, blobs and warps (due to avalanching) m>1 multi-armed wavelets and vortices (due to tau>1 radiation pressure instability) + many other possible causes

33. FEATURESin disks:(9) blobs, clumps ￭(5) streaks, feathers ￭(4) rings (axisymm) ￭(2) rings (off-centered) ￭(7) inner/outer edges ￭(5) disk gaps ￭(4) warps,uneven walls ￭(7) spirals, quasi-spirals￭(8) tails, extensions ￭(6) THEIR ORIGIN:(11) ￭ instrumental artifacts, variable PSF, noise, deconvolution etc. ￭ background/foreground obj. ￭ planets (gravity) ￭ stellar companions, flybys ￭ dust migration in gas ￭ dust blowout, avalanches ￭ episodic release of dust ￭ ISM (interstellar wind) ￭ stellar wind, magnetism ￭ collective eff. : self-gravity or the tau > 1 instability LOTS OF CONNECTIONS (~50) !