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Sternentstehung - Star Formation

Sternentstehung - Star Formation. Sommersemester 2006 Henrik Beuther & Thomas Henning. 24.4 Today: Introduction & Overview 1.5 Public Holiday: Tag der Arbeit 8.5 --- 15.5 Physical processes, heating & cooling, cloud thermal structure

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Sternentstehung - Star Formation

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  1. Sternentstehung - Star Formation Sommersemester 2006 Henrik Beuther & Thomas Henning 24.4 Today: Introduction & Overview 1.5 Public Holiday: Tag der Arbeit 8.5 --- 15.5 Physical processes, heating & cooling, cloud thermal structure 22.5Physical processes, heating & cooling, cloud thermal structure (H. Linz) 29.5 Basic gravitational collapse models 5.6 Public Holiday: Pfingstmontag 12.6 Basic gravitational collapse models 19.6 Accretion disks 26.6 Molecular outflow and jets 3.7 Protostellar evolution, the stellar birthline 10.7 Cluster formation and the Initial Mass Function 17.7 Massive star formation, summary and outlook 24.7 Extragalactic star formation More Information and the current lecture files: http://www.mpia.de/homes/beuther/lecture_ss06.html beuther@mpia.de

  2. M51: The Whirlpool Galaxy

  3. M51: The Whirlpool Galaxy

  4. Andromeda CO(2-1) Optical

  5. Mid-Infared view of part of Galactic plane

  6. 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

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

  8. Orion

  9. 1.2mm dust cont. Near-Infrared The Star-Forming Region W43 Optical

  10. Planck's Black Body

  11. Planck's Black Body

  12. 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)

  13. Hertzsprung-Russel diagram Main sequence: L=4pR2sbT4 Stefan-Boltzmann law

  14. r=105cm-3 Free-fall time scale: tff = (3p/32Gr)1/2 ------> 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 Hertzsprung-Russel diagram

  15. Properties of Main Sequence Stars Mass Sp. Type Lum Teff tMS [Msun] [log(Lsun)] [log(K)] [yr] O5 5.90 4.65 3.4x106 O6 5.62 4.61 4.3x106 O9 4.99 4.52 8.1x106 B2 3.76 4.34 2.6x107 B8 2.26 4.08 1.6x108 2 A5 1.15 3.91 1.1x109 G2 0.04 3.77 1.0x1010 0.8 K0 -0.55 3.66 2.5x1010 0.2 M5 -2.05 3.52 >1011 } greater than age of universe tMS ~ 5x10-4 Mc2/L = 1x1010 (M[Msun])/(L[Lsun]) yr

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

  17. The cosmic cycle

  18. Properties of Molecular Clouds Type n Size T Mass [cm-3] [pc] [K] [Msun] Giant Molecular Cloud 102 50 15 105 Dark Cloud Complex 5x102 10 10 104 Individual Dark Cloud 103 2 10 30 Dense low-mass cores 104 0.1 10 10 Dense high-mass cores >105 0.1-1 10-30 100-1000

  19. 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)

  20. Lyman a at 1216 A o The Interstellar Medium I Atomic Hydrogen 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

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

  22. cm mm submm The Interstellar Medium III Ionized gas • - H2 recombination lines from optical to cm wavelengths • Emission lines from heavier elements --> derive atomic abundances • He/H 0.1 • C/H 3.4x10-4 • N/H 6.8x10-5 • O/H 3.8x10-4 • Si/H 3.0x10-6 • - Free-free emission between e- and H+

  23. Optical Near-Infrared Interstellar dust: Extinction Dust composition: Graphite C Silicon carbide SiC Enstatite (Fe,Mg)SiO3 Olivine (Fe,Mg)2SiO4 Iron Fe Magnetite Fe3O4 Size distribution: Between 0.005 and 1mm n(a) ~ a-3.5 (a: size) (Mathis, Rumpl, Nordsieck 1977) Extinction dims and reddens the light

  24. 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.

  25. Pol. E B Dust polarization and magnetic fields Dust Molecular filaments can collapse along their magnetic field lines. Polarized submm continuum emission

  26. Star Formation Paradigm

  27. Sternentstehung - Star Formation Sommersemester 2006 Henrik Beuther & Thomas Henning 24.4 Today: Introduction & Overview 1.5 Public Holiday: Tag der Arbeit 8.5 --- 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 5.6 Public Holiday: Pfingstmontag 12.6 Basic gravitational collapse models 19.6 Accretion disks 26.6 Molecular outflow and jets 3.7 Protostellar evolution, the stellar birthline 10.7 Cluster formation and the Initial Mass Function 17.7 Massive star formation, summary and outlook 24.7 Extragalactic star formation More Information and the current lecture files: http://www.mpia.de/homes/beuther/lecture_ss06.html beuther@mpia.de

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