1 / 23

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.

ernie
Télécharger la présentation

Formation des filaments dans le milieu interstellaire

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related