1. Understanding the extrasolar planetary systems : observations & theories of disks and planets Pawel Artymowicz U of Toronto 1. Beta Pictoris and other dusty disks in planetary systems 2. Planet formation: are there really still two scenarios? 3. Discovery of the first 160+ planetary systems 4. Migration type I-III 5. Origin of structure in the dust and gas disks How to find this talk online: either google up “pawel”, or get directly planets.utsc.utoronto.ca/~pawel/UofA.ppt

2. Gen.Rel. Radiation transfer Thermodynamics of gas Stellar Astrophysics Disk theory Astrophysics of planetary systems Astronomy:observations of circumstellar disks Dynamics incl. Hydrodynamics and statics Nuclear physics High energ physics. meteoritics IDPs & zodiacal disk radioisotopes materials atmosph. Geo- chem

3. Gen.Rel. Radiation transfer Thermodynamics of gas Stellar Astrophysics of planetary systems Astronomy:observations of circumstellar disks, radial velocity exoplanets Dynamics, hydrodynamics and hydrostatics Nuclear physics High ener. physics. meteoritics radioisotopes materials atmosph. Geo- chem Disk theory IDPs, zodiacal light disks

4. First milestone in search for planetary systems was detection of dust around normal stars : Vega phenomenon Chemistry/mineralogy/crystallinity of dust Astrochemical unity of nature

5. Infrared excess stars (Vega phenomenon)

6. Beta Pictoris thermal radiation imaging (10 um) Lagage & Pantin (1993)

7. 1984 1993 Beta Pictoris, visible scattered starlight comparison with IR data yields a high albedo, A~0.4-0.5 (like Saturn’s rings but very much unlike the black particles of cometary crust or Uranus’ rings).

8. Small dust is observed due to its large total area Parent bodies like these (asteroids, comets) are the ultimate sources of the dust, but remain invisible in images due to their small combined area Comet

9. Optical thickness: perpendicular to the disk in the equatorial plane (percentage of starlight scattered and absorbed, as seen by the outside observer looking at the disk edge-on, aproximately like we look through the beta Pictoris disk)

10. What is the optical thickness ? It is the fraction of the disk surface covered by dust: here I this example it’s about 2e-1 (20%) - the disk is optically thin ( = transparent, since it blocks only 20% of light) picture of a small portion of the disk seen from above Examples: beta Pic disk at r=100 AU opt.thickness~3e-3 disk around Vega opt.thickness~1e-4 zodiacal light disk (IDPs) solar system ~1e-7

11. Vertical optical thickness  Vertical profile of dust density Radius r [AU]Height z [AU] STIS/Hubble imaging (Heap et al 2000) Modeling (Artymowicz,unpubl.): parametric, axisymmetric disk cometary dust phase function

12. Dust processing: collisions 1. Collisional time formula 2. The analogy with the early solar system (in the region of today’s TNOs = trans-Neptunian objects, or in other words, Kuiper belt objects, KBOs; these are asteroid-sized bodies up to several hundred km radius)

13. Time between collisions (collisional lifetime) of a typical meteoroid. Obviously, inversly proportional to the optical thickness (doubling the optical depth results in 2-times shorter particle lifetime, because the rate of collision doubles). P = orbital period, depends on radius as in Kepler’s III law. This formula is written with a numerical coefficion of 1/8 so as to reproduce the fact that a disk made of equal-sized particles needs to have the optical thickness of about 1/4 to make every particle traversing it vertically collide with some disk particle, on average. The vertical piercing of the disk is done every one-half period, because particles are on inclined orbits and do indeed cross the disk nearly vertically, if on circular orbits. If the orbits are elliptic, a better approximate formula has a coefficient of 12 replacing 8 in the above equation.

14. How does the Vega-phenomenon relate to our Solar System (Kuiper belt, or TNOs - transneptunian objects)

18. Evidence of planetesimals and planets in the vicinity of beta Pictoris: 1. Lack of dust near the star (r<30AU) 2. Spectroscopy => Falling Evaporating Bodies 3. Something large (a planet) needed to perturb FEBs so they approach the star gradually. 4. The disk is warped somewhat, like a rim of cowboy hat, which requires the gravitational pull of a planet on an orbit inclined by a few degrees to the plane of the disk. 5. Large reservoir of parent (unseen) bodies of dust needed, of order 100 Earth masses of rock/ice. Otherwise the dust would disappear quickly, on the collisional time scale

19. This is how disks look a decade later - much better quality data, fewer artifacts, disks appear smoother.

21. HST/WFPC2 camera a fantastic large-scale view of beta Pictoris out to r ~800 AU

22. Beta Pictoris 11 micron image analysis converting observed flux to dust area (Lagage & Pantin 1994) B Pic b(?) sky? Evidence of large bodies (planetesimals, comets?)

23. FEB = Falling Evaporating Bodies hypothesis in Beta Pictoris absorption line(s) that move on the time scale of days as the FEBs cross the line of sight H & K calcium absorption lines are located in the center of a stellar rotation-broadened line FEB star

24. Microstructure of circumstellar disks: identical with IDPs (interplanetary dust particles) mostly Fe+Mg silicates (Mg,Fe)SiO 3 (Mg,Fe) 2 SiO 4

25. A rock is a rock is a rock… which one is from the Earth? Mars? Beta Pic? It’s hard to tell from remote spectroscopy or even by looking under a microscope!

26. What minerals will precipitate from a solar-composition, cooling gas? Mainly Mg/Fe-rich silicates and water ice. Planets are made of precisely these things. Silicates silicates ices T(K) Chemical unity of nature… and it’s thanks to stellar nucleosynthesis! EQUILIBRIUM COOLING SEQUENCE

27. Crystallinity of minerals Recently, for the first time observations showed the difference in the degree of crystallinity of minerals in the inner vs. the outer disk parts. This was done by comparing IR spectra obtained with single dish telescopes with those obtained while combining several such telescopes into an interferometric array (this technique, long practiced by radio astronomers, allows us to achieve very good, low-angular resolution, observations). In the following 2 slides, you will see some “inner” and “outer” disk spectra - notice the differences, telling us about the different structure of materials: amorphous silicates = typical dust grains precipitating from gas, for instance in the interstellar medium, no regular crystal structure crystalline grains= same chemical composition, but forming a regular crystal structure, thought to be derived from amorphous grains by some heating (annealing) effect at temperatures up to ~1000 K.

29. ~90% amorphous ~95% crystalline ~45% amorphous compare ~60% amorphous Beta Pic,

30. That was good, but people wanted PLANETS Structures in dusty disks (footprints in the sand) Indirect but almost direct: periodic, Keplerian red+blueshifts in stellar spectra, or timing of pulsars Direct imaging Transits

31. Pulsar planets: PSR 1257+12 B 2 Earth-mass planets and one Moon-sizes one found around a millisecond pulsar First extrasolar planets discovered by Alex Wolszczan [pron.: Volshchan] in 1991, announced 1992, confirmed 1994 Name: PSR 1257+12 A PSR 1257+12 B PSR 1257+12 C M.sin 0.020 ± 0.002 M E 4.3 ± 0.2 M E 3.9 ± 0.2 M E Semi-major axis: 0.19 AU 0.36 AU 0.46 AU P(days): 25.262±0.003, 66.5419± 0.0001,98.2114±0.0002 Eccentricity: 0.0 0.0186 ± 0.00020.0252 ± 0.0002 Omega (deg): 0.0 250.4 ± 6 108.3 ± 5 The pulsar timing is so exact, observers now suspect having detected a comet!

32. Pulsar planets: PSR 1257+12 B 2 Earth-mass planets and one Moon-sizes one found around a millisecond pulsar A B C m: 0.020 M E 4.3 M E 3.9 M E a: 0.19 AU 0.36 AU 0.46AU e: 0 0.0186 0.0252 O: 0.0 250.4 108.3 First extrasolar planets discovered by Alex Wolszczan [pron.: Volshchan] in 1991, announced 1992, confirmed 1994 +comets ??

33. Radial-velocity planets around normal stars

35. -450: Extrasolar systems predicted (Leukippos, Demokritos). Formation in disks -325 Disproved by Aristoteles 1983: First dusty disks in exoplanetary systems discovered by IRAS 1992: First exoplanets found around a millisecond pulsar (Wolszczan & Dale) 1995: Radial Velocity Planets were found around normal, nearby stars, via the Doppler spectroscopy of the host starlight, starting with Mayor & Queloz, continuing wth Marcy & Butler, et al.

36. Orbital radii + masses of the extrasolar planets (picture from 2003) These planets were found via Doppler spectroscopy of the host’s starlight. Precision of measurement: ~3 m/s Hot jupiters Radial migration

38. Like us? NOT REALLY

39. Marcy and Butler (2003)

40. ~2003 2005

41. m sin i vs. a Zones of avoidance? multiple single

42. m sin i vs. a Zones of avoidance? Result: a----m

43. Eccentricity of exoplanets vs. a and m sini m, a, e somewhat correlated: a e ? m a e ? m a e ? m

44. Eccentricity of exoplanets vs. a and m sini m, a, e somewhat correlated: a e ? m a e ? m a e ? m

46. Gravitational Instability and the Giant Gaseous Protoplanet hypothesis

47. Gravitational stability requirements Local stability of disk, spiral waves may grow Local linear instability of waves, clumps form, but their further evolution depends on equation of state of the gas.

48. From: Laughlin & Bodenheimer (2001) Disk in this SPH simulation initially had Q ~ 1.5 > 1 The m-armed global spiral modes of the form grow and compete with each other. But the waves in a stable Q~2 disk stop growing and do not form small objects (GGPs).

49. Clumps forming in a gravitationally unstable disk (Q < 1) Recently, Alan Boss revived the half-abandoned idea of disk fragmentation GGPs?

50. Two examples of formally unstable disks not willing to form objects immediately Durisen et al. (2003) Break-up of the disk depends on the equation of state of the gas, and the treatment of boundary conditions.

51. Simulations of self-gravitating objects forming in the disk (with grid-based hydrodynamics) shows that rapid thermal cooling is crucial Armitage and Rice (2003) Disk not allowed to cool rapidly (cooling timescale > 1 P) Disk allowed to cool rapidly (on dynamical timescale, <0.5 P)

52. SPH = Smoothed Particle Hydrodynamics with 1 million particles Mayer, Quinn, Wadsley, Stadel (2003) Isothermal (infinitely rapid cooling)

53. GGP (Giant Gaseous Protoplanet) hypothesis = disk fragmentation scenario (A. Cameron in the 1970s) Main Advantages: forms giant planets quickly, avoids possible timescale paradox; planets tend to form at large distances amenable to imaging. MAIN DIFFICULTIES: 1. Non-axisymmetric and/or non-local spiral modes start developing not only at Q<1 but already when Q decreases to Q~1.5…2 They redistribute mass and heat the disk => increase Q (stabilize disk). 2. Empirically, this self-regulation of the effects of gravity on disk is seen in disk galaxies, all of which have Q~2 and yet don’t split into many baby gallaxies. 3. The only way to force the disk fragmentation is to lower Q~c/Sigma by a factor of 2 in just one orbital period. This seems impossible. 4. Any clumps in disk (e.g. A. Boss’ clumps) may in fact shear and disappear rather than form bound objects. Durisen et al. Have found that the equation of state and the correct treatment of boundary conditions are crucial, but could not confirm the fragmentation except in the isothermal E.O.S. case. 5. GGP is difficult to apply to Uranus and Neptune; final masses: Brown Dwarfs not GGPs 6. Does not easily explain core masses of planets and exoplanets, nor the chemical correlations (to be discussed in lecture L23)

54. Video of density waves in a massive protoplanetary disk The shocks at the surface are suggested as a way to heat solids and form chondrules, small round grains inside meteorites. Durisen and Boss (2005)

55. Envelope instability in proto- giants (nucleated gas accretion)

56. Comparison of gas and rock masses (in M E ) in giant planets and exoplanets (1980s) Planet Core mass Atmosph. Total mass Radius _________(rocks, M E )___(gas,_M E ) ____(M E ) _______( R J ) _ Jupiter 0-10 ~313 318 1.00 Saturn 15-20 ~77 95 0.84 Uranus 11-13 2 - 4 14.6 0.36 Neptune 13-15 2 - 4 17.2 0.34 core envelope (atmosphere)

57. Comparison of gas and rock masses (in M E ) in giant planets and exoplanets (Oct. 2005) Planet Core mass Atmosph. Total mass Radius _________(rocks, M E )___(gas,_M E ) ____(M E ) _______( R J ) _ Jupiter 0-10 ~313 318 1.00 Saturn 15-20 ~77 95 0.84 Uranus 11-13 2 - 4 14.6 0.36 Neptune 13-15 2 - 4 17.2 0.34 HD 209458b ~0 ~220 204- 235 1.32 ± 0.05 (disc. 1999) HD 149026b ~ 70 ~45 105-124 0.73 ± 0.03 (disc. 7/2005) HD 189733b ~10-20(?) ~350 351-380 1.26 ± 0.03 (disc. 10/2005) core envelope (atmosphere) ? ?

58. Standard Accumulation Scenario

59. Two-stage accumulation of planets in disks

60. M core =10 M E (?) => contraction of the atmosphere and inflow of gas from the disk Planetesimal = solid body >1 km (issues not addressed in the standard theory so far)

61. How many planetesimals formed in the solar nebula?

62. Core-atmosphere instability above a critical core mass Mizuno (1980), Bodenheimer (1980s), Stevenson (1986) Planetesimals supply heat of accretion L = GM/R c ( dM/dt) Convection and radiation carry that luminosity away as dictated by equations of stellar stucture. Low-mass cores have tenuous hydrogen-helium dominated envelopes that smoothly join the surrounding disk. Opacity of the atmosphere and L have a major influence on the envelope mass. When M core = M atm, the hydrostatic equations of stellar structure no longer have solutions. The critical core mass (above which no equilibrium is possible) depends on opacity K and luminosity L as M crit ~ (K L)^(- 3/4) M crit ~ 8-20 M E in our solar system, perhaps different in others

63. Upsilon Andromedae And the question of planet-planet vs. disk planet interaction

64. The case of Upsilon And examined: Stable or unstable? Resonant? How, why?...

65. Upsilon Andromedae’s two outer giant planets have STRONG interactions Inner solar system (same scale)

67. . Definition of logitude of pericenter (periapsis) a.k.a. misalignment angle

68. In the secular pertubation theory, semi-major axes (energies) are constant (as a result of averaging over time). Eccentricities and orbit misalignment vary, such as to conserve the angular momentum and energy of the system. We will show sets of thin theoretical curves for (e2, dw). [There are corresponding (e3, dw) curves, as well.] Thick lines are numerically computed full N-body trajectories. Classical celestial mechanics

69. eccentricity Orbit alignment angle 0.8 Gyr integration of 2 planetary orbits with 7th-8th order Runge-Kutta method Initial conditions not those observed!

70. Upsilon And: The case of very good alignment of periapses: orbital elements practically unchanged for 2.18 Gyr unchanged

71. N-body (planet-planet) or disk-planet interaction? Conclusions from modeling Ups And 1. Secular perturbation theory and numerical calculations spanning 2 Gyr in agreement. 2. The apsidal “resonance” (co-evolution) is expected and observed to be strong, and stabilizes the system of two nearby, massive planets 3. There are no mean motion resonances 4. The present state lasted since formation period 5. Eccentricities in inverse relation to masses, contrary to normal N-body trend tendency for equipartition. Alternative: a lost most massive planet - very unlikely 6. Origin still studied, Lin et al. Developed first models involving time-dependent axisymmetric disk potential

72. Diversity of exoplanetary systems likely a result of: cores? disk-planet interactiona m e (only medium) yes planet-planet interactiona m? e yes star-planet interactiona m e? yes disk breakup (fragmentation into GGP) a m e? Metallicity no X X X X XX X X

73. : resonances and waves in disks, orbital evolution Disk-planet interaction This part of the lecture is more advanced and optional (not required for the exam, for instance) If you are skipping it, please go directly to the last slide.

76. ... SPH (Smoothed Particle Hydrodynamics) Jupiter in a solar nebula (z/r=0.02) launches waves at LRs. The two views are (left) Cartesian, and (right) polar coordinates.

77. Inner and Outer Lindblad resonances in an SPH disk with a jupiter

80. Illustration of nominal positions of Lindblad resonances (obtained by WKB approximation. The nominal positions coincide with the mean motion resonances of the type m:(m+-1) in celestial mechanics, which doesn’t include pressure.) Nominal radii converge toward the planet’s semi-major axis at high azimuthal numbers m, causing problems with torque calculation (infinities!). On the other hand, the pressure-shifted positions are the effective LR positions, shown by the green arrows. They yield finite total LR torque.

81. Wave excitation at Lindblad resonances (roughly speaking, places in disk in mean motion resonance, or commensurability of periods, with the perturbing planet) is the basis of the calculation of torques (and energy transfer) between the perturber and the disk. Finding precise locations of LRs is thus a prerequisite for computing the orbital evolution of a satellite or planet interacting with a disk. LR locations can be found by setting radial wave number k_r = 0 in dispersion relation of small-amplitude, m-armed, waves in a disk. [Wave vector has radial component k_r and azimuthal component k_theta = m/r] This location corresponds to a boundary between the wavy and the evanescent regions of a disk. Radial wavelength, 2*pi/k_r, becomes formally infinite at LR.

83. --> m(z/r) Eccentricity pumping Eccentricity in type-I situation is always strongly damped.

84. Conclusion about eccentricity: As long as there is some gas in the corotational region (say, +- 20% of orbital radius of a jupiter), eccentricity is strongly damped. Only if and when the gap becomes so wide that the near-lying LRs are eliminated, eccentricity is excited. (==> planets larger than 10 m_jup were predicted to be on eccentric orbits (Artymowicz 1992). In practice, this may account for intermediate-e exoplanets. For extremely high e’s we need N-body explanation: perturbations by stars, or other planets.

86. Disk-planet interaction: numerics

87. Mass flows through the gap opened by a jupiter-class exoplanet ==> Superplanets can form Mass flows despite the gap. This result explains the possibility of “superplanets” with mass ~10 M J Migration explains hot jupiters.

88. Binary star on circular orbit accreting from a circumbinary disk through a gap. Surface density Log(surface density) An example of modern Godunov (Riemann solver) code: PPM VH1-PA. Mass flows through a wide and deep gap!

89. AMR PPM (Flash) simulation of a Jupiter in a standard solar nebula. 5 levels/subgrids. (Peplinski and Artymowicz 2004)

90. What does the permeability of gaps teach us about our own Jupiter: - Jupiter was potentially able to grow to 5-10 m j, if left accreting from a standard solar nebula for ~1 Myr - the most likely reason why it didn’t: the nebula was already disappearing and not enough mass was available.

91. Variable-resolution PPM (Piecewise Parabolic Method) [Artymowicz 1999] Jupiter-mass planet, fixed orbit a=1, e=0. White oval = Roche lobe, radius r_L= 0.07 Corotational region out to x_CR = 0.17 from the planet disk gap (CR region)

92. 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.

93. How can there be ANY SURVIVORS of the rapid type-III migration?! Migration type III Structure in the disk: gradients od density, edges, gaps, dead zones Migration stops, planet grows/survives

94. Edges or gradients in disks: Magnetic cavities around the star Dead zones

95. Unsolved problem of the Last Mohican scenario of planet survival in the solar system: Can the terrestial zone survive a passage of a giant planet? §N-body simulations, N~1000 (Edgar & Artymowicz 2004) §A quiet disk of sub-Earth mass bodies reacts to the rapid passage of a much larger protoplanet (migration speed = input parameter). §Results show increase of velocity dispersion/inclinations and limited reshuffling of material in the terrestrial zone. §Migration type III too fast to trap bodies in mean- motion resonances and push them toward the star §Evidence of the passage can be obliterated by gas drag on the time scale passage of a pre- jupiter planet(s) not exluded dynamically.

97. 1. Early dispersal of the primordial nebula ==> no material, no mobility 2. Late formation (including Last Mohican scenario)

98. Origin of structure in dusty disks:

99. Source: P. Kalas HD107146

100. Disk of Alpha Pisces Austrini (a PsA) = Fomalhaut a bright southern star type A

101. A new edge- on disk! NICMOS/ HST (Schneider et al 2005) near-IR band (scattered light) This is how disks look when just discovered

102. HD 141569A is a Herbig emission star >2 x solar mass, >10 x solar luminosity, hydrogen emission lines H are double, because they come from a rotating inner gas disk. CO gas has also been found at r = 90 AU. Observations by Hubble Space Telescope (NICMOS near-IR camera). Age ~ 5 Myr, a transitional disk Gap-opening PLANET ? So far out?? TYPE III MIGRATION? R_gap ~350AU dR ~ 0.1 R_gap

103. HD 14169A disk gap confirmed by new observations (HST/ACS)

105. Summary of the various effects of radiation pressure of starlight on dust grains in disks: alpha particles = stable, orbiting particles on circular & elliptic orbits beta meteoroids = particles on hyperbolic orbits, escaping due to a large radiation pressure

106. Radiation pressure coefficient (radiation pressure/gravity force) of an Mg-rich pyroxene mineral, as a function of grain radius s. s

107. Above a certain beta value, a newly created dust particle, released on a circular orbit of its large parent body (beta=0) will escape to infinity along the parabolic orbit. What is the value of beta guaranteeing escape? It’s 0.5 (see problem 1 from set #5). We call the physical radius of the particle that has this critical beta parameter a blow-out radius of grains. From the previous slide we see that in the beta Pictoris disk, the blow-out radius is equal ~2 micrometers. Observations of scattered light, independent of this reasoning show that, indeed, the smallest size of observed grains is s~2 microns. Particles larger but not much larger than this limit will stay in the disk on rather eccentric orbit.

108. How radiation pressure induces large eccentricity: = F rad / F grav

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

110. Structure formation in dusty disks

111. The danger of overinterpretation of structure Are the PLANETS responsible for EVERYTHING we see? Are they in EVERY system? Or are they like the Ptolemy’s epicycles, added each time we need to explain a new observation?

112. FEATURES in disks: (9 types) blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals ￭ tails, extensions ￭ ORIGIN: (10 categories) ￭ 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 UV, wind, magnetism ￭ collective effects (radiation in opaque media, selfgravity) (Most features additionally depend on the viewing angle)

113. AB Aur : disk or no disk? Fukugawa et al. (2004) another “Pleiades”-type star no disk

114. Source: P. Kalas ?

115. Hubble Space Telescope/ NICMOS infrared camera

116. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals ￭ tails, extensions ￭ ORIGIN: ￭ planets (gravity)

117. .

118. Some models of structure in dusty disks rely on too limited a physics: ideally one needs to follow: full spatial distribution, velocity distribution, and size distribution of a collisional system subject to various external forces like radiation and gas drag -- that’s very tough to do! Resultant planet depends on all this. Beta = 0.01 (monodisp.)

119. Dangers of fitting planets to individual frames/observations: Vega has 0, 1, or 2 blobs, depending on bandpass. What about its planets? Are they wavelength- dependent too!? 850 microns

120. HD 141569A is a Herbig emission star >2 x solar mass, >10 x solar luminosity, Emission lines of H are double, because they come from a rotating inner gas disk. CO gas has also been found at r = 90 AU. Observations by Hubble Space Telescope (NICMOS near-IR camera). Age ~ 5 Myr, a transitional disk Gap-opening PLANET ? So far out?? R_gap ~350AU dR ~ 0.1 R_gap

121. Outward migration of protoplanets to ~100AU or outward migration of dust to form rings and spirals may be required to explain the structure in transitional (5-10 Myr old) and older dust disks

122. HD141569+BC in V bandHD141569A deprojected HST/ACS Clampin et al.

123. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals ￭ tails, extensions ￭ ORIGIN: ￭ stellar companions, flybys

124. Beta = 4 H/r = 0.1 M gas = 50 M E Best model, Ardila et al (2005) involved a stellar fly-by & HD 141569A 5 M J, e=0.6, a=100 AU planet

125. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals ￭ tails, extensions ￭ ORIGIN: ￭ dust migration in gas

126. In the protoplanetary disks (tau  ) dust follows gas. Sharp features due to associated companions: stars, brown dwarfs and planets. These optically thin transitional disks (tau <1) must have some gas even if it's hard to detect. Warning: Dust starts to move w.r.t. gas! Look for outer rings, inner rings, gaps with or without planets. These replenished dust disk are optically thin (tau<<1) and have very little gas. Sub-planetary & planetary bodies can be detected via spectroscopy, spatial distribution of dust, but do not normally expect sharp features. Extensive modeling including dust-dust collisions and radiation pressure needed Planetary systems: stages of decreasing dustiness  Pictoris 1 Myr 5 Myr 12-20 Myr

127. Gas pressure force vgvg v=v K v vgvg

128. Migration: Type 0 §Dusty disks: structure from gas-dust coupling (Takeuchi & Artymowicz 2001) §theory will help determine gas distribution Gas disk tapers off here Predicted dust distribution: axisymmetric ring

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

130. Dust avalanches and implications: -- upper limit on dustiness -- the division of disks into gas-rich, transitional and gas-poor

131. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals ￭ tails, extensions ￭ ORIGIN: ￭ dust blowout avalanches, ￭ episodic/local dust release

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

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

134. 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 almost the most dusty, gas-poor disk, possible. the midplane optical thickness Ratio of the infrared luminosity (IR excess radiation from dust) to the stellar luminosity; it gives the percentage of stellar flux absorbed reemitted thermally multiplication factor of debris in 1 collision (number of sub-blowout debris) Avalanche growth equation Solution of the avalanche growth equation

135. f IR =f d disk dustiness OK! Age paradox! Gas-free modeling leads to a paradox ==> gas required or episodic dust production

136. Bimodal histogram of fractional IR luminosity f IR predicted by disk avalanche process

137. source: Inseok Song (2004)

138. ISO/ISOPHOT data on dustiness vs. time Dominik, Decin, Waters, Waelkens (2003) uncorrected ages corrected ages ISOPHOT ages, dot size ~ quality of age ISOPHOT + IRAS f d of beta Pic -1.8

139. transitional systems 5-10 Myr age

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

141. Grigorieva, Artymowicz and Thebault (to be subm. to A&A 2005) Comprehensive model of dusty debris disk (3D) with full treatment of collisions and particle dynamics. ￭ especially suitable to denser transitional disks supporting dust avalanches ￭ detailed treatment of grain-grain colisions, depending on material ￭ detailed treatment of radiation pressure and optics, depending on material ￭ localized dust injection (e.g., planetesimal collision) ￭ dust grains of similar properties and orbits grouped in “superparticles” ￭ physics: radiation pressure, gas drag, collisions Results: ￭ beta Pictoris avalanches multiply debris x (3-5) ￭ spiral shape of the avalanche - a robust outcome ￭ strong dependence on material properties and certain other model assumptions

143. Model of (simplified) collisional avalanche with substantial gas drag, corresponding to 10 Earth masses of gas in disk

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

145. In gas+dust disks which are optically thick in the radial direction there may be an interesting set of instabilities. 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 Forces of rad. pressure relative to those on the center of the arm

146. In gas+dust disks which are optically thick in the radial direction there may be an interesting set of instabilities. 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. effective coefficient for coupled gas+dust r (this profile results from dust migration)

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

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

149. r 1 Effective Q number (radiation+selfgravity) Analogies with gravitational instability ==> similar structures (?)

150. FEATURES in disks:(9 types) blobs, clumps ￭ (5) streaks, feathers ￭ (4) rings (axisymm) ￭ (2) rings (off-centered) ￭ (7) inner/outer edges ￭ (5) disk gaps ￭ (4) warps ￭ (7) spirals, quasi-spirals ￭ (8) tails, extensions ￭ (6) ORIGIN: (10 reasons) ￭ 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) Many (~50) possible connections !

151. Not only planets but also Gas + dust + radiation => non-axisymmetric features including regular m=1 spirals, conical sectors, and multi-armed wavelets Conclusion: