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