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Formation des filaments dans le milieu interstellaire

Formation des filaments dans le milieu interstellaire. Patrick Hennebelle. Molecular clouds and Map of spectra. Hily-Blant & Falgarone. Structure functions in molecular clouds (Hily-Blant et al. 2008). Polaris (Kosmas). Taurus (IRAM). Polaris (IRAM). S p. S 3. SL94. K41.

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Formation des filaments dans le milieu interstellaire

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  1. Formation des filaments dans le milieu interstellaire Patrick Hennebelle

  2. Molecular clouds and Map of spectra Hily-Blant & Falgarone

  3. Structure functions in molecular clouds (Hily-Blant et al. 2008) Polaris (Kosmas) Taurus (IRAM) Polaris (IRAM) Sp S3 SL94 K41 Boldyrev et al. 2002

  4. Structure functions in simulations of molecular clouds

  5. Orion A large diversity of observed filaments… cores DR21 Dutrey et al 91 Polaris from the goult belt survey André et al. 2010 Schneider et al 10

  6. A large diversity of simulated filaments… Hennebelle et al 08 Padoan et al 01 Heitsch et al 08 Vazquez-Semadeni et al. 11 Li & Nakamura 08 Inoue et al 09

  7. How to form a filament ? Compression of two of the axis: shock or gravity Extension of one of the axis: Shear (the very heart of turbulence)

  8. Dense cores are density fluctuations induced by turbulence (and not by gravity) 3D density field velocity field (norm) A turbulent molecular cloud (Mach 10). Includes the magnetic field (supercritical) but not gravity. Proposition: filaments are intersection of shocked sheets Padoan et al. 01

  9. Comparison between hydro and MHD simulations Decaying turbulence, 2 phase-medium, no gravity, 5 cm-3 Initial Mach (wrt cold gas) : 10, B=0 or 5 mG HYDRO MHD

  10. Aspect ratio of clumps denser than 200 cm-3 HYDRO MHD shortest/longest shortest/longest MHD simulations are more filamentary while magnetic field should reduce the strength of the shocks… intermediate/longest intermediate/longest

  11. Impact of an initial shear No turbulence initially HYDRO MHD

  12. Impact of an initial shear Mach 5 turbulence initially MHD HYDRO MHD case is more filamentary because magnetic field gives more coherence to the flow. It connects fluid particles and keep a memory.

  13. Correlation between the principal axis of the clumps and the principal axis of the shear tensor hydro a mhd

  14. Hydrodynamical MHD

  15. A filament from the MHD simulations aligned with the shear Courtesy Edith Falgarone

  16. Fragmentation of sheet into filaments Classical Jeans analysis: The largest mode (k=0) has the fastest growth rate. Could be a problem for forming filaments by gravity but things are different for a self-gravitating sheet. Linear stability of the self-gravitating sheet (Spitzer 78, Nagai et al. 98) idem: but for: more unstable mode = typical width of the filaments : Dispersion relation => Fragmentation of a sheet into filaments

  17. Fragmentation of sheet into filament Exact Equilibrium Solutions in 2D (Schmid-Burgk 1976, Myers 2009) Fragmentation of a sheet into filaments Filaments

  18. Gravitational amplification of anisotropies (Lin et al. 71)

  19. Formation of filaments by gravitational amplification Gravity No turbulence Gravity Turbulence +MHD Gravity Turbulence

  20. Formation of filament in gravo-turbulent simulations Evolution of the density field of a molecular cloud The calculation (SPH technique) takes gravity into account but not the magnetic field. Turbulence induced the formation of filaments, which become self-gravitating and collapse Klessen & Burkert 01

  21. Comparaisons Observations 30m/Simulations « Best-fit» Simulation Peretto et al. 2007 Diag. PV N2H+(101-012) 30m Continuum 1.2mm 30m 10 Vitesse (km.s-1) 2km.s-1 9 CMM4 CMM2 CMM3 CMM2 CMM3 CMM4 8 50 0 -50 Position (arcsec) 7 Diag. PV simulé 30m Carte colonne densité simulée 30m 6 5 Vitesse (km.s-1) 2km.s-1 SIM3 SIM1 SIM2 SIM4 SIM3 SIM2 SIM4 SIM2 SIM3 -100 50 0 -50 Position (arcsec) 0.5 pc

  22. Comparaisons Observations PdBI Peretto et al. 2007 Diag. PV N2H+(101-012) PdBI Continuum 3.2mm PdBI 30m+PdBI CMM4 Vitesse (km.s-1) CMM13 10 CMM2 CMM3 9 CMM13 CMM2 CMM3 CMM4 8 50 0 -50 Position (arcsec) 7 Diagramme PV simulé PdBI Carte colonne densité simulée PdBI 6 5 + + + + + Vitesse (km.s-1) + + SIM4 SIM2 SIM2 SIM13 SIM1 SIM3 SIM4 SIM13 SIM3 SIM2 SIM3 SIM4 50 0 -50 Position (arcsec)

  23. Conclusion

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