1. Sternentstehung - Star Formation
Sommersemester 2006
Henrik Beuther & Thomas Henning
24.4 Today: Introduction & Overview
Public Holiday: Tag der Arbeit
15.5 Physical processes, heating & cooling, cloud thermal structure
22.5 Physical processes, heating & cooling, cloud thermal structure (H. Linz)
29.5 Basic gravitational collapse models
Public Holiday: Pfingstmontag
12.6 Basic gravitational collapse models
19.6 Accretion disks
26.6 Molecular outflow and jets
Protostellar evolution, the stellar birthline
10.7 Cluster formation and the Initial Mass Function
Massive star formation, summary and outlook
Extragalactic star formation
More Information and the current lecture files:

2. M51: The Whirlpool Galaxy

3. M51: The Whirlpool Galaxy

4. Andromeda
CO(2-1) Optical

6. Mid-Infared view of part of Galactic plane

7. Giant Molecular Clouds
Sizes: 20 to 100pc; Masses: 104 to 106 Msun; Temperatures: 10 to 15K
Superesonic velocity dispersion ~2-3 km/s mainly due to turbulence
Magnetic field strengths of the order 10mG
Average local densities ~104cm-3; Volume-averaged densities ~102cm-3
--> highly clumped material

8. Sites of Star Formation
Optical Near-Infrared
Masses:
Between fractions and a
few 100 solar masses
Densities:
Of the order 106cm-3
1.2 mm Dust Continuum C18O N2H+

9. Orion

10. The Star-Forming Region W43
Optical
Near-Infrared
1.2mm dust cont.

11. Planck's Black Body

12. Planck's Black Body

13. Wien's Law max = 2.9/T [mm] Examples:
The Sun T 6000 K  max= 480 nm (optical)
Humans T 310 K  max= 9.4 mm (MIR)
Molecular Clouds T 20 K  max= 145 mm (FIR/submm)
Cosmic Background T 2.7 K  max= 1.1 mm (mm)

14. Hertzsprung-Russel diagram
Main sequence: L=4pR2sbT Stefan-Boltzmann law

15. Hertzsprung-Russel diagram
Free-fall time scale: tff = (3p/32Gr)1/ > tff ~ 105 yr
Contraction of protostar under gravity releasing energy as radiation:
Virial theorem: Epot + 2Ekin = 0 --> Ekin = 0.5Epot = GM2/R
---> Kelvin-Helmhotz time scale: tKH = Ekin/L = GM2/RL
~ 107 yr for the sun
r=105cm-3

16. Properties of Main Sequence Stars
Mass Sp. Type Lum Teff tMS
[Msun] [log(Lsun)] [log(K)] [yr]
O x106
O x106
O x106
B x107
B x108
A x109
G x1010
K x1010
M >1011
} greater
than age of
universe
tMS ~ 5x10-4 Mc2/L = 1x1010 (M[Msun])/(L[Lsun]) yr

17. Sun
The easiest to see
in night sky and
distant galaxies

19. The cosmic cycle

20. Properties of Molecular Clouds
Type n Size T Mass
[cm-3] [pc] [K] [Msun]
Giant Molecular Cloud
Dark Cloud Complex x
Individual Dark Cloud
Dense low-mass cores
Dense high-mass cores >

21. Molecules in Space
atoms
H C c-C3H C C5H C6H CH3C3N CH3C4H CH3C5N? HC9N CH3OC2H5 HC11N
AlF C2H l-C3H C4H l-H2C4 CH2CHCN HCOOCH3 CH3CH2CN (CH3)2CO
AlCl C2O C3N C4Si C2H CH3C2H CH3COOH? (CH3)2O NH2CH2COOH?
C C2S C3O l-C3H2 CH3CN HC5N C7H CH3CH2OH CH3CH2CHO
CH CH C3S c-C3H2 CH3NC HCOCH H2C HC7N
CH+ HCN C2H CH2CN CH3OH NH2CH CH2OHCHO C8H
CN HCO CH2D+? CH 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)

22. The Interstellar Medium I
Atomic Hydrogen
Lyman a
at 1216 A o
The 21cm line arises when the
electron spin S flips from parallel
(F=1) to antiparallel (F=0)
compared to the Proton spin I.
DE = 5.9x10-5 eV

23. The Interstellar Medium II
Molecular Hydrogen
Carbon monoxide CO Formaldehyde H2CO Cyanoacetyline HC3N
Excitation mechanisms:
Rotation > usually cm and (sub)mm wavelengths
Vibration > usually submm to FIR wavelengths
- Electronic transitions --> usually MIR to optical wavelengths

24. The Interstellar Medium III
Ionized gas
- H2 recombination lines from optical to cm wavelengths
Emission lines from heavier elements --> derive atomic abundances
He/H
C/H x10-4
N/H x10-5
O/H x10-4
Si/H x10-6
- Free-free emission between e- and H+
cm mm submm

25. Interstellar dust: Extinction
Optical Near-Infrared
Dust composition:
Graphite C
Silicon carbide SiC
Enstatite (Fe,Mg)SiO3
Olivine (Fe,Mg)2SiO4
Iron Fe
Magnetite Fe3O4
Size distribution:
Between and 1mm
n(a) ~ a (a: size)
(Mathis, Rumpl, Nordsieck 1977)
Extinction dims and reddens the light

26. S(n) = N (s/D2) Q(n) B(n,T)
Colour: MIR
Contours: mm continuum
Interstellar dust: Thermal emission
S(n) = N (s/D2) Q(n) B(n,T)
With N dust grains of cross section s at a distance D, a dust emissivity
Q~n2 and the Planck function B(n,T). In the Rayleigh-Jeans limit, we have
S(n) ~ n4
The thermal dust emission is
optically thin and hence directly
proportional to the dust column
density. With a dust to gas mass
ratio of ~1/100, we can derive
the gas masses.

27. Dust polarization and magnetic fieldsB
Pol. E
Dust
Molecular filaments can collapse
along their magnetic field lines.
Polarized submm continuum emission

28. Star Formation Paradigm

29. Sternentstehung - Star Formation
Sommersemester 2006
Henrik Beuther & Thomas Henning
24.4 Today: Introduction & Overview
Public Holiday: Tag der Arbeit
15.5 Physical processes, heating & cooling, cloud thermal structure
22.5 Physical processes, heating & cooling, cloud thermal structure (H. Linz)
29.5 Basic gravitational collapse models
Public Holiday: Pfingstmontag
12.6 Basic gravitational collapse models
19.6 Accretion disks
26.6 Molecular outflow and jets
Protostellar evolution, the stellar birthline
10.7 Cluster formation and the Initial Mass Function
Massive star formation, summary and outlook
Extragalactic star formation
More Information and the current lecture files: