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The coagulation, fragmentation and radial drift of dustin protoplanetary disks F. Brauer, C. Dullemond, Th. Henning
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 .
Step I- Coagulation at a certain radius No radial motion, no fragmentation Step II - plus radial motion of the dust Step III - plus fragmentation What is this talk about? Question: Can planetesimals form by dust particle coagulation? (To give an impression about dust particle growth)
Disk r • We consider a turbulent disk The disk model - An initial dust to gas ratio of 10-2
Coagulation at a fixed radiusNo fragmentationNo radial motion of the dust Step I
1 - Brownian motion 2 - Differential settling 3 - Turbulent coagulation One word about growth mechanisms We will consider 3 different growth mechanisms:
km size bodies The initial distribution cm size particles The particle distribution after 1 Myrs ( Coagulation / NO radial drift / NO fragmentation )
- In a protostellar disk the dust particles drift inward • We adopt the radial drift of individual particles in our model Region of fast radial drift Which particles drift so fast? One word about the radial drift of the dust A maximum radial drift of some 10 meters per second
No km size bodies No cm size bodies Maximum radial drift line The particle distribution after 1 Myrs ( Coagulation + radial drift / No fragmentation )
Change some disk parameters? How do we get larger particles?
Maximum radial drift line Changing the dust to gas ratio - Particle distribution after 103 yrs ( Coagulation + radial drift / NO fragmentation )
• Shattering results Small grains collide with larger bodies Between equally large bodies One word about fragmentation • Fragmentation velocity : 10 m/s • Complete destruction & Cratering
Maximum radial drift Maximum radial drift The particle distribution after 103 yrs ( Coagulation + radial drift + fragmentation ) Dust to gas ratio of 0.05
3 things to take away 1 - The dust to gas ratio is a highly important disk parameter. 2 - The dust can grow beyond the radial drift barrier for dust to gas ratios not much higher than 0.01. 3- The dust can grow beyond the fragmentation barrier for low turbulent disks. (Even though I do not show that here) Conclusions It is possible to form planetesimals by coagulation. (Even though it is quite difficult)