Transcript 30.4 Gravitational collapse & early protostellar evolution I (HB)

Star and Planet Formation
Sommer term 2007
Henrik Beuther & Sebastian Wolf
16.4 Introduction (H.B. & S.W.)
23.4 Physical processes, heating and cooling, radiation transfer (H.B.)
30.4 Gravitational collapse & early protostellar evolution I (H.B.)
07.5 Gravitational collapse & early protostellar evolution II (H.B.)
14.5 Protostellar and pre-main sequence evolution (H.B.)
21.5 Outflows and jets (H.B.)
28.5 Pfingsten (no lecture)
04.6 Clusters, the initial mass function (IMF), massive star formation (H.B.)
11.6 Protoplanetary disks: Observations + models I (S.W.)
18.6 Gas in disks, molecules, chemistry, keplerian motions (H.B.)
25.6 Protoplanetary disks: Observations + models II (S.W.)
02.7 Accretion, transport processes, local structure and stability (S.W.)
09.7 Planet formation scenarios (S.W.)
16.7 Extrasolar planets: Searching for other worlds (S.W.)
23.7 Summary and open questions (H.B. & S.W.)
More Information and the current lecture files: http://www.mpia.de/homes/beuther/lecture_ss07.html
and http://www.mpia.de/homes/swolf/vorlesung/sommer2007.html
Emails: [email protected], [email protected]
Accretion disks
1.3mm
IRAS
NIR
1.3mm
IRAS
NIR
Full line: no inner whole
Dashed line: Inner whole
Beckwith et al. 1990
Early single-dish observations
toward T-Tauri stars revealed
cold dust emission.
In spherical symmetry this
would not be possible since
the corresponding gas and
dust would extinct any
emission from the central
protostar.
--> Disk symmetry necessary!
Simple case: flat, black disk
T ~ r-3/4, Ldisk ~ 1/4 L*
Model SEDs
Beckwith et al. 1996, 1999
Effects of gaps on disk SED
Full line: no gap
Long-dashed: gap 0.75 to 1.25 AU
Short-dashed: gap 0.5 to 2.5 AU
Dotted: gap 0.3 to 3 AU
To become detectable gap has to
cut out at least a decade of disk
size.
Additional FIR excess
- Larger inner or smaller outer disk radii even increase the discrepancy.
- Data indicate that outer disk region is hotter than expected from
flat, black disk model --> Disk flaring
Disk flaring
The scale height h of a disk increases with radius r because the thermal
energy decreases more slowly with increasing radius r than the vertical
component of the gravitational energy:
Evert, grav ~ h/r * GM*/r ~ Etherm ~ kT(r)
with T(r) ~ r-3/4
--> h ~ k/GM* r5/4
Hydrostatic equilibrium, radiative transfer
models for flared disks I
Chiang & Goldreich 1997
Hydrostatic equilibrium , radiative transfer
models for flared disks II
h
nvert ~ exp(z2/2h2)
Chiang & Goldreich 1997
Hydrostatic equlibrium, radiative transfer
models for flared disks III
Chiang & Goldreich 1997
Flat spectrum disks
Class I protostar
disk
Infalling
envelope
Outflow
cavity
Class II T Tauri star
- Flat-spectrum sources have too much flux
to be explained by heating of protostar only.
- In very young sources, they are still embedded
in infalling envelope --> this can scatter light
and cause additional heating of outer disk.
 Flat spectrum sources younger than typical
class II T Tauri stars.
Calvet et al. 1994, Natta et al. 1993
Molecules in Space
2
3
4
5
6
7
8
9
10
11
12
13 atoms
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------H2
C3
c-C3H
C5
C5H
C6H
CH3C3N
CH3C4H
CH3C5N?
HC9N
CH3OC2H5
HC11N
AlF
C2H
l-C3H
C4H
l-H2C4 CH2CHCN HCOOCH3 CH3CH2CN
(CH3)2CO
AlCl
C2O
C3N
C4Si
C2H4
CH3C2H
CH3COOH? (CH3)2O
NH2CH2COOH?
C2
C2S
C3O
l-C3H2 CH3CN HC5N
C7H
CH3CH2OH
CH3CH2CHO
CH
CH2
C3S
c-C3H2 CH3NC HCOCH3
H2C6
HC7N
CH+ HCN
C2H2
CH2CN CH3OH NH2CH3
CH2OHCHO C8H
CN
HCO
CH2D+? CH4
CH3SH c-C2H4O
CH2CHCHO
CO
HCO+
HCCN
HC3N
HC3NH+ CH2CHOH
CO+ HCS+
HCNH+ HC2NC HC2CHO
CP
HOC+ HNCO
HCOOH NH2CHO
CSi
H2O
HNCS
H2CHN C5N
HCl
H2S
HOCO+ H2C2O HC4N
KCl
HNC
H2CO
H2NCN
NH
HNO
H2CN
HNC3
NO
MgCN H2CS
SiH4
NS
MgNC
H3O+ H2COH+
NaCl
N2H+ NH3
OH
N2O
SiC3
PN
NaCN C4
SO
OCS
SO+
SO2
SiN
c-SiC2
SiO
CO2
SiS
NH2
CS
H3+
HF
SiCN
SH
AlNC
FeO(?) SiNC
Currently 129 detected interstellar molecules (from November 2005)
Molecules in disks
2
3
4
5
6
7
8
9
10
11
12
13 atoms
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------H2
C3
c-C3H
C5
C5H
C6H
CH3C3N
CH3C4H
CH3C5N?
HC9N
CH3OC2H5
HC11N
AlF
C2H
l-C3H
C4H
l-H2C4 CH2CHCN HCOOCH3 CH3CH2CN
(CH3)2CO
AlCl
C2O
C3N
C4Si
C2H4
CH3C2H
CH3COOH? (CH3)2O
NH2CH2COOH?
C2
C2S
C3O
l-C3H2 CH3CN HC5N
C7H
CH3CH2OH
CH3CH2CHO
CH
CH2
C3S
c-C3H2 CH3NC HCOCH3
H2C6
HC7N
CH+ HCN
C2H2
CH2CN CH3OH NH2CH3
CH2OHCHO C8H
CN
HCO
CH2D+? CH4
CH3SH c-C2H4O
CH2CHCHO
CO
HCO+
HCCN
HC3N
HC3NH+ CH2CHOH
CO+ HCS+
HCNH+ HC2NC HC2CHO
CP
HOC+ HNCO
HCOOH NH2CHO
CSi
H2O
HNCS
H2CHN C5N
HCl
H2S
HOCO+ H2C2O HC4N
KCl
HNC
H2CO
H2NCN
NH
HNO
H2CN
HNC3
NO
MgCN H2CS
SiH4
NS
MgNC
H3O+ H2COH+
NaCl
N2H+ NH3
OH
N2O
SiC3
PN
NaCN C4
SO
OCS
SO+
SO2
SiN
c-SiC2
SiO
CO2
SiS
NH2
CS
H3+
HF
SiCN
SH
AlNC
FeO(?) SiNC
DCO+
Currently 129 detected interstellar molecules (from November 2005)
Disk dynamics: Keplerian motion
Simon et al.2000
DM Tau
Guilloteau et al. 1998
For a Keplerian supported disk, centrifugal
force should equal grav. force.
Fcen = mv2/r = Fgrav = Gm*m/r2
--> v = (Gm*/r)1/2
Ohashi et al. 1997
Velocity
Non-Keplerian motion: AB Aur
- Central depression in
cold dust and gas
emission.
- Non-Keplerian velocity profile vr -0.4+-0.01
PdBI, Pietu et al. 2005
SMA, Lin et al. 2006
SMA, Lin et al. 2006
CO(3-2)
345GHz continuum
- Possible explanations
Formation of lowmass companion or
planet in inner disk.
Early evolutionary
phase where
Keplerian motion is
not established yet
(large envelope).
Disk-jet co-rotation in DG Tau
red
blue
Testi et al. 2002
Corotation of disk and jet
Bacciotti et al. 2002
Disk structure
Different lines
trace different
optical depth.
Pietu et al. 2007
Relatively robust results
- Disk sizes between 200 and 2000AU.
- Most disks are in Keplerian rotation.
- Temperature structure consistent with flared disk models and T at
CO disk surface (t=1) goes like T(r) ~ r-0.6.
- Vertical temperature gradients with cooler disk mid-plane.
- Disk temperature increase with increasing central stellar mass.
- Beyond 150AU, disks around low-mass stars have T<17K, therefore, CO
can freeze out on dusk grains.
Inner disk regions
Squares: gaseous inner
disk radii (CO fundamental)
Circles: dust inner disk
radii (interferometry
and SEDs)
Najita et al. 2007
- Mid-infrared emission lines of vibrationally excited CO traces gas > 1000K.
- The gas rotates at Keplerian velocity --> line-widths converts to inner disk
radii.
- Inner gas disk extends beyond disk sublimation radius and is close to
co-rotation radius (coupling of stellar magnetic field to disk).
Disks in massive star formation
IRAS18089-1732
Beuther & Walsh
Hot rotating structure
not in Keplerian motion.
IRAS20126+4104, Cesaroni et al. 1997, 1997, 2005
Keplerians disk around central protostar of ~7Msun
-
Still deeply embedded, large distances, clustered environment --> confusion
Current obs. status largely “Velocity gradient perpendicular to outflow”.
(Sub)mm interferometry important to disentangle the spatial confusion.
The right spectral line tracer still missing which can distinguish the disk
emission from the surrounding envelope emission.
Summary
Bergin et al. 2006
Star and Planet Formation
Sommer term 2007
Henrik Beuther & Sebastian Wolf
16.4 Introduction (H.B. & S.W.)
23.4 Physical processes, heating and cooling, radiation transfer (H.B.)
30.4 Gravitational collapse & early protostellar evolution I (H.B.)
07.5 Gravitational collapse & early protostellar evolution II (H.B.)
14.5 Protostellar and pre-main sequence evolution (H.B.)
21.5 Outflows and jets (H.B.)
28.5 Pfingsten (no lecture)
04.6 Clusters, the initial mass function (IMF), massive star formation (H.B.)
11.6 Protoplanetary disks: Observations + models I (S.W.)
18.6 Gas in disks, molecules, chemistry, keplerian motions (H.B.)
25.6 Protoplanetary disks: Observations + models II (S.W.)
02.7 Accretion, transport processes, local structure and stability (S.W.)
09.7 Planet formation scenarios (S.W.)
16.7 Extrasolar planets: Searching for other worlds (S.W.)
23.7 Summary and open questions (H.B. & S.W.)
More Information and the current lecture files: http://www.mpia.de/homes/beuther/lecture_ss07.html
and http://www.mpia.de/homes/swolf/vorlesung/sommer2007.html
Emails: [email protected], [email protected]