L 6: Circumstellar Disks
Background image: HH 30 JHK HST-NICMOS, courtesy Padgett et al. 1999, AJ 117, 1490
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
1
L 6: Circumstellar Disks
The Formation of Stars
Chapters: 11, 13
Background image: HH 30 JHK HST-NICMOS, courtesy Padgett et al. 1999, AJ 117, 1490
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
2
L 6: Circumstellar Disks
Recent reviews include:
Protostars & Planets IV, Mannings, Boss & Russell (eds.)
12 Articles on Disks
5 Articles on Outflows
Zuckerman,
ARAA 2001, 39: 549
Zuckerman & Song, ARAA 2004, 42: 685
Protostars & Planets V
rene@astro.su.se
(2005)
L6 - Stellar Evolution I: November-December, 2006
3
L 6: Circumstellar Disks
and Outflows
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
4
Flattened structures - Disks
Inevitable consequence of star formation
Rotation
Rotation
Magnetic Fields
Stahler & Palla : the centrifuga l radius
Eq.(10.50) assumes Shu collapse
 cen
1
2
 T    
  14 1 
 0.3 AU 
 10 K   10 s 
rene@astro.su.se
2
 t 
 5 
 10 yr 
3
L6 - Stellar Evolution I: November-December, 2006
5
Flattened structures - Disks
Inevitable consequence of star formation
Rotation
P.S. Laplace 1796, 1799
I. Kant 1755
Exposition du systeme du monde
Mechanique celeste
Allgemeine
Naturgeschichte und
Theorie des Himmels
Planetary System Formation
Astrobiology School: Q1+2 2007
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
6
Mass Loss - Outflows
Inevitable consequence of star formation
Angular Momentum Loss - Redistribution
The race between mass accretion & mass loss processses
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
7
Lynden-Bell & Pringle 1974, MNRAS 168, 603:
Keplerian Disk
Differential Rotation
+
Viscosity
rene@astro.su.se
Mass Transport Inwards
Angular Momentum Transport Outwards
L6 - Stellar Evolution I: November-December, 2006
8
`standard model´: e.g., Frank, King & Raine Accretion Power in Astrophysics
self-consistent structure of steady, optically thick a-disk
blackbody radiation and thin disk approximation

2 H
cs
1.  c 
2. H 
3. cs 
2
thi n disk definition
vertical hydrostati c equilibriu m
GM / R 3
P
veloci ty of sound (  1)

 kTc 4 4
4. Pc 

T
 m H 3c
4
4σTc
3GMM
5.

3
8 R 3
equation of state
1


2
R


1     
 R 


6.   
energy tra nsport
opacity relation
7
p q
e.g.,     T : Kramer opacity for p  1, q  0
2
1


2
R


1     
 R 


8.   a cs H
M
7.   
3
When / Where valid ?
mass and angular momentum conservati on
viscosity prescripti on
Shakura & Sunyaev : a  1,    turb  v turblturb
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
9
Example:
Lin & Papaloizou opacities
(1985 PP II):
Icy grains
HMolecules
bound-free
free-free
(Cox-Stuart-Alexander)
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
10
Grain Opacities
See Ph. Thebault’s lecture
rene@astro.su.se
Beckwith et al. 2000, PP IV
L6 - Stellar Evolution I: November-December, 2006
11
`standard model´: e.g., Frank, King & Raine Accretion Power in Astrophysics
self-consistent structure of steady, optically thick a-disk
Solve for the 8 unknowns ρ, Σ, H, cs , P, Tc , ,
as functions of M, M , R
and any parameter R , Rin , Rout , a ...
The radial drift velo city ist then found from

3   R 
v rad  
1  
2R   R 

and the spectrum
1
2
1


M
 

2 R 

4 h cos i 3 out
R dR
F  2

R exp( h / kT )  1
c D2
in
R
has the form
3  h / kT
 e
rene@astro.su.se


1
3

  2T
L6 - Stellar Evolution I: November-December, 2006
12
40 observed SEDs of T Tauri Stars & `mean model´ of star+disk
HABE Disk Structure:
Dullemond & Dominik 2004
includes
vertical
Temperature
distribution
D´Alessio et al. 1999
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
13
Gas Disks – Structure Models
Steady Disks around Single Stars
Boundary Conditions
Rin : boundary layer, magnetosphere, hole?
Rout: ad hoc? , interstellar turbulence?
Viscosity
MHD/rotation
Opacity
  (, T, …, XYZ, ..., z0, ..., c ...)
Models
Adams & Shu 1986 (flat)
Kenyon & Hartmann 1987 (flared)
Malbet & Bertout 1991 (vertical structure)
D´Allessio et al. 1998,... 2003
Aikawa & Herbst 1998 (chemistry)
Nomura 2002 (2D)
Wolf 2003 (3D)
See G. Mellema’s lecture
[examples]
rene@astro.su.se
(Hawley & Balbus 1995)
L6 - Stellar Evolution I: November-December, 2006
14
Observations of Keplerian Disks
JE Keeler 1895
ApJ 1: 416
The Rings of Saturn
spectrum
image
Courtesy Brandeker, Liseau & Ilyn 2002
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
15
2 Categories of Disks observed
T Tauri Disks: around young stars
(0.1 - 10 Myr)
of half a solar mass
(0.1 - 1 Msun)
at 150 pc distance
(50 - 450 pc)
in and/or near molecular clouds
gas rich
Accretion Disks
Debris Disks: around young ms-stars (10 - 400 Myr)
of about a solar mass
(1 - 2 Msun)
at 20 pc distance
(3 - 70 pc)
in the general field
gas poor
Vega-excess stellar disks
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
16
Frequency of Disks
High Rate of occurence around young stars
NGC 2024
Trapezium cluster
IC 348
86%
80%
65%
Haisch et al. 2001
65%
Muench et al. 2001
and around
BDs in Trapezium cluster
see also G. Gahm’s lecture
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
17
Gas Disks - Sizes
Size scale (AU)
20000
5000 - 10000
1400
<500
45 + 1600
200
7000
5000
4000 - 6000
1200
4000
5000
2500
10
20000
Tracer (mode)*
CS (1- 0) (S)
13CO (1- 0) (S)
C18O (1- 0) (I)
1.4 mm (I)
mm, cm (I)
0.8 mm (I)
H13CO+ (1- 0) (S)
0.7 - 1 mm (S)
C18, 17O (2- 1) (S)
13CO (1- 0) (I)
H13CO+ (1- 0) (I)
H12, 13CO+ (1- 0) (S, I)
C18O+ (1- 0) (I)
7 mm (I)
Reference
Kaifu et al. 1984
Fridlund et al. 1989
Sargent et al. 1988
Woody et al. 1989
Keene & Masson 1990
Lay et al. 1994
Mizuno et al. 1994
Ladd et al. 1995
Fuller et al. 1995
Ohashi et al. 1996
Saito et al. 1996
Hogerheijde et al.1997, 98
Momose et al. 1998
Rodriguez et al. 1998
CH3OH (2-1), (5-4) (S) White et al. 2006
*S=single dish, I=Interferometer
rene@astro.su.se
Fridlund et al. 2002
for
One Object: L1551
Size depends on frequency/mode of observation
L6 - Stellar Evolution I: November-December, 2006
18
Gas Disks - Sizes
generally
T Tauri/HABE disks
50 - 100 AU
Dust: mm-continuum interferometry
100 - 300 AU
Dust: scattered stellar light
300 AU
Gas: CO lines (evidence for Kepler rotation)
Silhouettte disks (``proplyds´´)
up to 1000 AU
rene@astro.su.se
Dust: scattered stellar light
L6 - Stellar Evolution I: November-December, 2006
19
Gas Disks - Masses
continuum
H2
Gas
Directly
CO
and
Dust
blueshifted CO
redshifted CO
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
20
? Why ?
Gas Disks - Masses
Lower limit: 0.001 to 1 MSun
gas
(based on mm / submm continuum)
dust
+dust
How good are these numbers ?
Do we understand disks ?
Solar Minimum Mass Nebula = 0.002 MSun
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
21
Gas Disks - Make up
gas disks consist of gas and dust
what components?
what proportions?
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
22
2 T Tauri Disks - Make up
13CO
CO (200)
(1)*
HCO+
HCO+ (200)
(5)
HCN (200)
HCN (5)
*(N) = depletion factor
LkCa 15
rene@astro.su.se
TW Hya
van Zadelhoff 2002
L6 - Stellar Evolution I: November-December, 2006
23
2 T Tauri Disks - Chemistry
Molecular abundances (rel. H2)
Species
LkCa 15
TW Hya
CO
HCO+
H13CO+
DCO+
CN
HCN
H13CN
HNC
DCN
CS
H2CO
CH3OH
N 2H +
H 2D +
3.4 ( - 7)
5.6 (-12)
< 2.6(-12)
….
2.4 (-10)
3.1 (-11)
….
….
….
8.5 (-11)
4.1 (-11)
< 3.7(-10)
< 2.3(-11)
< 1.5(-11)
5.7 ( - 8)
2.2 (-11)
3.6 (-13)
7.8 (-13)
1.2 (-10)
1.6 (-11)
< 8.4(-13)
< 2.6(-12)
< 7.1(-14)
….
< 7.1(-13)
< 1.9(-11)
< 1.8(-11)
< 7.8(-12)
Thi 2002
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
24
Gas Disks - Evolution
Time scales (viscous accretion disk)
tdyn ~ a ttherm ~ a (H/R)2 tvisc
tdyn ~ 1/Kepler
a ~ 10-3 - 10-2
H/R << 1
if T ~ R-1/2
, tvisc ~ R
tvisc ~ 105 yr (a/0.01)-1 (R/10 AU)
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
25
Gas Disks - Evolution
Disk dispersal and disk lifetimes
SE = Stellar Encounter
(tidal stripping)
WS = Stellar wind
stripping
evap E = photoevaporation
external star
evap c = photoevaporation
central star
All for Trapezium conditions
T ~ R-0.5 , tvisc ~ R
tvisc ~ 105 yr (a/0.01)-1 (R/10 AU)
rene@astro.su.se
Physical Mechanisms
Hollenbach et al. 2000 PPIV
L6 - Stellar Evolution I: November-December, 2006
26
Gas (T Tauri) Disks - Evolution
Disk dispersal and disk lifetimes
Average Error Bar
Mass accretion evolution
Calvet et al. 2000 PPIV
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
27
Gas Disks to Debris Disks – Evolution ?
How ?
fdust = DLIR/L
vs
stellar age
See also lecture by Ph. Thebault
(F)IR - excess
Stellar luminosity
(bolometric)
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
28
Gas Disks to Debris Disks – Evolution ?
Clusters
Individual stars
(= 1 zodi)
Spangler et al. 2001
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
29
HD 21362
HR 4796A
b Pic
 t 1
24 m Spitzer data
266 ms stars
 t 2
Rieke et al. 2005, ApJ 620, 1010
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
30
Debris Disks - Properties
debris (collision products) or particulate (gas free)
percentage of Main Sequence stars (15%?)
(observationally) biased towards Spectral Type A
for (detectable) ages <400 Myr Habing et al. 1999, 2001
disk sizes
100 to 2000 AU
disk masses
>1 to 100 MMoon (small grains)
see Ph. Thebault’s lecture
Pre-IRAS
Solar system Zodi
Vega
rene@astro.su.se
US Navy Chaplain G. Jones 1855 AJ 4, 94
Blackwell et al. 1983
L6 - Stellar Evolution I: November-December, 2006
31
rene@astro.su.se
http://www.hep.upenn.edu/~davidk/bpic.html
L6 - Stellar Evolution I: November-December, 2006
32
How much Gas in Dusty Debris Disks ?
Disk evolution hypothesis: gas-rich to gas-poor
Census of material (mgas/mdust): planet formation
planet formation:
enough gas for GPs ?
planet formation:
time scales ?
planet formation:
seeds of Life ?
See
astrobiology
lecture
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
33
Putting it all together
Outflows
Infall
Disks
L 1551 IRS 5 - a protostellar binary
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
34
L 1551 IRS 5
Jet blue 10´´
Optical Image (NTT, R-band)
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
35
N: Bright and Fast
S: Faint and Slow
2 Jets !!! – HST-R + spectroscopy
Fridlund & Liseau 1998, ApJ 499, L75
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
36
Counter jet(s)
Also 2 Radio Jets – 3.5 cm VLA (arcsec)
Rodriguez et al. 2003, ApJ 586, L137
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
37
Proper Motion of Disk Sources -
VLA 2cm
Rodriguez et al. 2003, ApJ 583, 330
Dynamical mass of the IRS 5 system :
0.1   m, i   mD, i  1.2 M o
i
Disk masses
i
m
D, i
 0.1 M o ,
i
where
rene@astro.su.se
mD, N  2  mD,S
L6 - Stellar Evolution I: November-December, 2006
38
Surface luminositi es and effective temperatu res
 L

Teff, i   surf, i 2 
 4  Ri 
1
4
11
M

 M 
o i

Lsurf, i  Lrad, i  Lconv,i  L0
 LD, i
R 
 R 
o i

L0  0.153 Lo and max deuterium burning LD ( M )  curves
Stahler et al. - Stahler - Palla & Stahler
1980 through 1993
F. Palla, priv. communication
Mass-Radius relation
(M/R)
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
39
Putting it all together: observation + theory of infall + theory of mass loss
L 1551 IRS 5 - a protostellar binary
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
40
Putting it all together: observation + theory of infall + theory of mass loss
L 1551 IRS 5 - a protostellar binary
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
41
MHD x-wind models: ang. momentum parameter J
adapted from Liseau, Fridlund & Larsson 2005, ApJ, 619, 959
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
42
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
43
Stellar Atmosphere Models
rene@astro.su.se
Observed Spectrum (upper curves)
Combined Rotating Model (lower )
L6 - Stellar Evolution I: November-December, 2006
44
After collaps and /or main accretion phase:
Pre-main-sequence evolution begins...
... next lecture by G. Gahm
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
45
L 6: conclusions
• circumstellar disks are a consequence of star
formation
• disks and bipolar outflows/jets are connected
• disks form potentially planetray systems
L 6: open questions
• what are the physics of disks and their outflows ?
• how do disks evolve ?
• what fraction forms planetary systems ?
• when and how ?
rene@astro.su.se
L6 - Stellar Evolution I: November-December, 2006
46