Protostellar Disks: Birth, Life and Death

Neal Turner Jet Propulsion Laboratory, California Institute of Technology

Protostellar Disks: Protostellar Disks: Birth, Life and DeathBirth, Life and Death

National Aeronautics and Space Administration

The Life of Protostellar Disks

1. Jets and Winds2. Basic disk properties3. Angular momentum transport4. Evolution of the solids

Hartigan et a

l. 1995 / A

ntoniucci et al. 2008

McKee & Ostriker 2007

Pyo et al. 2005

Zinnecker et al. 1998

i et al. 2001

Burrow

s et al. 199

C. Lad

a 1985

Girart et al. 2006

ura et al. 1999

ay et al. 1997

Johns-Krull 2007

Ferreira et al. 2006

Spruit 1996National Aeronautics and Space Administration

Anderson et al. 2003

Size of the Launching Region?

Jet power = Rate of work done against the magnetic torque= (Footpoint orbital frequency) x (Angular momentum flux):

v p,∞2

2= Ω0ϖ∞vφ ,∞

Infer launching region lies 0.3 to 4 AU from the star.

Assumes energy and momentum conserved along streamlines.

Y. Kato 2004

Outflow-Driven Turbulence 1

Outflow-Driven Turbulence 2

Cloud kinetic energy vT2 dissipates on a crossing time R/vT, so

the outflows can provide the stirring if

With R=10 pc, vT=10 km s-1, f=0.01, vJ=300 km s-1 and jet mass flow rate 10-7 Solar masses per year,

the outflows are sufficient to power the turbulence.

i.e., if the outflow kinetic luminosity is greater than the dissipation rate in the gas associated with the star.

J vJ2 >

Basic Disk Properties

Hartmann & Kenyon 1996National Aeronautics and Space Administration

M. Simon et al. 2000

Andrews & Williams 2007National Aeronautics and Space Administration

Origins of the Surface Density Profile

In steady-state Shakura-Sunyaev -disk,

αT~ R−1

if irradiation controls the temperature profile.

Weidenschillin

g 1977

Dullemond et al. 2007National Aeronautics and Space Administration

Bergin et al. 2007National Aeronautics and Space Administration

K. R. Bell et al. 1995National Aeronautics and Space Administration

Hartmann et al. 1993National Aeronautics and Space Administration

Angular Momentum Transport

1. Gravitational Instability1. Gravitational Instability

Small disturbances grow if

mie 2001

Mejia et al. 2005

With slower cooling, instability leads to sustained accretion.

Balbus &

ley 1991

albus & H

awley 1991

Three Ways to Lose Magnetic Flux

Ionization ProcessesIonization Processes

Stellar X-Rays

Interstellar Cosmic Rays

Long-Lived Radionuclides

At 1 AU in the minimum mass

Solar nebula

Midplane ionisation is weak!

Short-Lived Radionuclides

Wardle 2007National Aeronautics and Space Administration

MRI turbulence requires

1 m Grains

No Grains

H. Li et al. 2001

Lodato & Clarke 2004National Aeronautics and Space Administration

Evolution of the Solids

van Boekel et al. 20

TEM image of a thin-sectioned Wild 2 grain consisting of enstatite with exsolution lamellae of diopside, formed from a melt (H. Leroux)

Natta et al. 20

ResolvedUnresolved

Furlan et al. 200

A Rough Estimate of Grain Growth Timescales

Particles settle at the terminal speed, with the force of gravity balancing the force of the gas molecules striking from below:

Particles remain compact spheres.

Particles grow by sweeping up smaller, stationary grains:

dt= vsett =

ρcsσ

dt=10−2 ρvsettσ

Settling Only

Settling & Sweeping

Particle growth: extreme cases

Ballistic Particle-Cluster Agglomeration

ballistic hit-and-stick impacts of single dust particles into growing

dust agglomerate

Ballistic Cluster-Cluster Agglomeration

ballistic hit-and-stick collisions between equal-mass dust

agglomerates

i = 1,024 i = 1,024From J. Blum

BPCAN=2

From J. Blum

BPCAN=4

From J. Blum

BPCAN=8

From J. Blum

BPCAN=16

From J. Blum

BPCAN=32

From J. Blum

BPCAN=64

From J. Blum

BPCAN=128

From J. Blum

BPCAN=256

From J. Blum

BPCAN=512

From J. Blum

BPCAN=1024

From J. Blum

BCCAN=2

From J. Blum

BCCAN=4

From J. Blum

BCCAN=8

From J. Blum

BCCAN=16

From J. Blum

BCCAN=32

From J. Blum

BCCAN=64

From J. Blum

BCCAN=128

From J. Blum

BCCAN=256

From J. Blum

BCCAN=512

From J. Blum

BCCAN=1024

From J. Blum

Radial Drift

Hot, Dense

Cold, Less

Radial Drift

Hot, Dense

Cold, Less

Dense€

vφ2 = vK

≈ vK2 − cs

vφ ≈ 1−H 2

⎝ ⎜

⎠ ⎟vK

Radial Drift

Hot, Dense

Cold, Less

Grain v=vK

Weidenschilling &

Cuzzi 1993

1 AU in MMSN

Non-fractal Aggregate Growth

(Hit-and-Stick)

Cratering/Fragmentatio

Non-fractal Aggregate Sticking + Compaction

Cratering/Fragmen-tation/Accretion

tickin

Growth

Stick)

Restructuring/Compaction

EXPERI

/Accre

Erosion

COMPILATION

Diameter

100 µm

1 µm 100 m100 µm 1 cm 1 m

Non-fractal Aggregate Growth

(Hit-and-Stick)

Erosion

tickin

/Accre

Cratering/Fragmentatio

Growth

Stick)

Restructuring/Compaction

Non-fractal Aggregate Sticking + Compaction

Cratering/Fragmen-tation/Accretion

on Mass

Mass conservation

Mass gain

* for compact

targets only

Blum & Wurm 2008

Barranco 2008

Stirring by Kelvin-Helmholtz Instability

Stirring by Magneto-Rotational Turbulence

Turner et al. 2006

Johansen et al. 2007

The Life of Protostellar Disks

1. Jets and Winds2. Basic disk properties3. Angular momentum transport4. Evolution of the solids

Protostellar Disks: Birth, Life and Death

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Transcript of Protostellar Disks: Birth, Life and Death

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