structures in illuminated, optically thick dust disks pawel artymowicz , jeffrey fung
DESCRIPTION
Structures in illuminated, optically thick dust disks Pawel Artymowicz , 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. HD 141596. FEATURES in disks:(9) - PowerPoint PPT PresentationTRANSCRIPT
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Structures in illuminated, optically thick dust disks
Pawel Artymowicz, Jeffrey Fung
U of Toronto
1.Origin of the observed structure in disks2.Disks with structure but without planets
Signposts of Planets GSFC, 18 Oct. 2011
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HD 141596
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FEATURES in 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) !
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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)1
Age paradox
Coloreffects
Limit on fIRin gas-free disks
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Structure in dusty disks
Overinterpreted observations
(noise, backgroundobjects)
Dust-gas interaction: axisym. rings (Takeuchi
and Artymowicz 2001) Create large gaps!
Dust avalanches,
optical thickness <<1but > ( LIR/L*. ~ 3e-3)
Optical thickness > 1non-axisymmetric
instabilities
Planetsand other perturbers
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Outward Migration of Jupiter-like planet in a MMSN-like disk.
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Outward migration type IIIof 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 showsradius in the range (0.5-5) a
Full range of azimuthson the vertical axis.
Time in units of initialorbital period.
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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 * <#debris/collision>)
N
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The above example is relevant to HD141569A, a prototype transitional disk with interesting quasi-spiral structure. Conclusion:
60
2
1
2
10~)20exp(~)exp(/
10~
2.0018.0)1.0(
)/(
)2/()/()/(
)2/()4/(2
NNN
NNdN
N
fzrso
rdrzrdrs
rdrrrdrf
IR
IR
Transitional disks MUST CONTAIN GAS or face self-destruction.Beta Pic is among the most dusty, gas-poor disks, 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, then re-emitted thermally
multiplication factor of debris in 1 collision (number of sub-blowout debris)
Simplified avalanche equation
Solution of the simplified avalanche growth equation
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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
fd of beta Pic = maximum dustiness of disks
-1.8
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Grigorieva, Artymowicz and Thebault (A&A, 2007)Comprehensive model of dusty debris disk (3D) with full treatmentof collisions and particle dynamics.
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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
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Structure in dusty disks
Overinterpreted observations
(noise, backgroundobjects)
Dust-gas interaction: axisym. rings (Takeuchi
and Artymowicz 2001)
Dust avalanches,
optical thickness <<1but > ( LIR/L*. ~ 3e-3)
Optical thickness > 1non-axisymmetric
instabilities
Planetsand other perturbers
![Page 14: Structures in illuminated, optically thick dust disks Pawel Artymowicz , Jeffrey Fung](https://reader035.vdocuments.mx/reader035/viewer/2022081520/5681675e550346895ddc2ec4/html5/thumbnails/14.jpg)
Theory of the tau>1 instability in disks.
Axisymmetric diskof opaque gas
or
dust w/shadowing
Point source of gravity
radiationpressure on gas/dust
Ingredients of the instability:
Isn’t it stable?..
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Radiation pressureon 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 forceor self-gravity. The instability is thus pseudo-gravitational in natureand 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 relativeto those on the center of the arm
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The instability is thus pseudo-gravitational in natureand can be obtained from a WKB local analysis.
ekGif
ek
ierf
eik
r
e
dr
gravityself
tmkriKrad
tmkri
tmkri
1
)(10
)(10
)(10
0
0
00
4
)1(
)(
10....1.0~
)exp()exp(
0
effective coefficient for coupled gas+dust
r
(this profile results from outward dust migration;Chiang & Murray-Clay 2007;Dominik & Dullemond 2011did not consider coagulation)
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ekGif
ek
ierf
eik
r
e
dr
gravityself
tmkriKrad
tmkri
tmkri
1
)(10
)(10
)(10
0
0
00
4
)1(
)(
10....1.0~
)exp()exp(
0
Step function of r or constant
)( tmkri (WKB)
2
kGif
Gikf
GffffeqPoissonG
11
11
111
2
44
4exp(...).4
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ekGif
ek
ierf
eik
r
e
dr
gravityself
tmkriKrad
tmkri
tmkri
1
)(10
)(10
)(10
0
0
00
4
)1(
)(
10....1.0~
)exp()exp(
0
Step function of r or constant
)( tmkri (WKB)
2
kGif
Gikf
GffffeqPoissonG
11
11
111
2
44
4exp(...).4
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00
0)(2
11
,11
/)()(
.)(1;
0
rrdec
GQ
yinstabilitgravQc
GQ
r
sorb
sorb
r1
Effective Q number(selfgravity + radiation)
Analogies with gravitational instability ==> similar structures (?)
2
Previously just this inverse Safronov-Toomre number
Now:
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tau = 2, beta = 0.2
0 180 deg 360 deg
radius
.7
1
1.6
azimuthal angle
Free particles casting shadows
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tau = 4, beta = 0.2
0 180 deg 360 deg
radius
.7
1
1.6
azimuthal angle
Free particles casting shadows
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tau = 12, beta = 0.2
0 180 deg 360 deg
radius
.7
1
1.6
azimuthal angle
Free particles casting shadows
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Beta = 0.2
De Val Borro& Artymowicz(2008, unpubl.),
FLASH hydrocode
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Beta = 0.2
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Beta = 0.2
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tau = 3beta = 0.075
PPM
gas disk density
soundspeed c/vk = 0.05
Navier-Stokesviscosity: alpha = 0
radius
Azi
mut
hal a
ngle
(0-3
60 d
eg)
1 2 3(2a)
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tau = 4beta = 0.15
PPM
gas disk density
soundspeed c/vk = 0.05
Navier-Stokesviscosity: alpha = 0
radius
Azi
mut
hal a
ngle
(0-3
60 d
eg)
1 2 3(3a)
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NOT
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nVidia GeForcegraphics processors
CPU=Intel4-core
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nVidia CUDA = extended C-language for GPU programmingup to 5 TFLOP/s using one computer
Cudak1 2 TFLOP, 484 coresCudak2 3 TFLOP , 724 coresCudak3 5+ TFLOP, 1444 cores all: max 10+ TFLOP, 2652 cores
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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!
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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
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FEATURES in 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) !