The coagulationThe coagulation, , fragmentation and radial fragmentation and radial
drift of dustdrift of dust in in protoplanetary disksprotoplanetary disks
F. Brauer, C. Dullemond, Th. Henning
Who am I?Who am I?
Born march 14th 1980 in Eisenach (Thüringen)
Studied physics in Jena 1999-2005
Diploma in Quantum theory (2005)
Hopefully PhD in 2008
Main hobby .
What is this talk about?What is this talk about?
Step IStep I - Coagulation at a certain radius - Coagulation at a certain radius
No radial motion, no fragmentationNo radial motion, no fragmentation
Step IIStep II - plus radial motion of the dust - plus radial motion of the dust
Step IIIStep III - plus fragmentation - plus fragmentation
Question:
Can planetesimals form by dust particle coagulation?
(To give an impression about dust particle growth)
The disk modelThe disk model
DiskDisk
r
- We consider a turbulent disk
- An initial dust to gas ratio of 10-2
Coagulation at a fixed radiusCoagulation at a fixed radius
NoNo fragmentation fragmentationNoNo radial motion of the dust radial motion of the dust
Step I
One word about growth mechanisms One word about growth mechanisms
We will consider 3 different growth mechanisms:
1 - Brownian motion
2 - Differential settling
3 - Turbulent coagulation
The initial distribution
The particle distribution after 1 MyrsThe particle distribution after 1 Myrs( Coagulation / NO radial drift / NO fragmentation )
km size bodies
cm size particles
Coagulation + radial drift/mixingCoagulation + radial drift/mixing
NoNo fragmentation fragmentation
Step II
One word about the radial drift of the dust One word about the radial drift of the dust
A maximum radial drift of
some 10 meters per second
- In a protostellar disk the dust particles drift inward
- We adopt the radial drift of individual particles in our model
Which particles drift so fast?
Region of fast radial drift
Maximum radial drift line
The particle distribution after 1 MyrsThe particle distribution after 1 Myrs( Coagulation + radial drift / No fragmentation )
No km size bodies
No cm size bodies No cm size bodies
Change some disk parameters?Change some disk parameters?
How do we get larger particles?How do we get larger particles?
Changing the dust to gas ratio - Changing the dust to gas ratio - Particle distribution after 10Particle distribution after 1033 yrs yrs
( Coagulation + radial drift / NO fragmentation )
Maximum radial drift line
Coagulation Coagulation + radial drift/mixing+ radial drift/mixing
+ fragmentation+ fragmentation
Step III
One word about fragmentationOne word about fragmentation• Fragmentation velocity : 10 m/s
• Shattering results
• Complete destruction & Cratering
Small grains collide with larger bodiesBetween equally large bodies
Dust to gas ratio of 0.05Dust to gas ratio of 0.05
Maximum radial drift
Maximum radial drift
The particle distribution after 10The particle distribution after 1033 yrs yrs( Coagulation + radial drift + fragmentation )
1 1 - The dust to gas ratio is a highly important disk parameter.
3 things to take away3 things to take away
2 - The dust can growcan grow beyond the radial drift barrier for dust to gas ratios not much higher than 0.01.
3 - The dust can can growgrow beyond the fragmentation barrier for low turbulent disks. (Even though I do not show that here)
ConclusionsConclusions
It is possible to form planetesimals by coagulation.
(Even though it is quite difficult)(Even though it is quite difficult)
Thank you for your attentionThank you for your attention