1 / 24

Multiphase medium in molecular clouds

Douglas Lin Dept of Astronomy & Astrophysics, Univ California, Santa Cruz Kavli Institute for Astronomy & Astrophysics , Peking University in collaboration with Tingtao Zhou , Xu Huang, Matthias Gritschneder , Stephen Murray, Andi Burkert.

druce
Download Presentation

Multiphase medium in molecular clouds

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. Douglas Lin Dept of Astronomy & Astrophysics, Univ California, Santa Cruz KavliInstitute for Astronomy & Astrophysics, Peking University in collaboration with Tingtao Zhou, Xu Huang, Matthias Gritschneder, Stephen Murray, AndiBurkert Multiphase medium in molecular clouds Cosmological Streaming: Inflows & Outflows Jerusalem, Dec 15th, 2011 22 slides

  2. Region of star formation - M16 T. A. Rector & B. A. Wolpa, NOAO, AURA McCaughrean & Andersen 2002, A&A, 389, 513

  3. Molecular cloud: Pipe Nebula Starless cores embedded in Pipe Nebula Pressure equilibrium with the surrounding warm medium Lada et al 2008 Similarity between CMF & IMF CMF as the provenance of IMF 3/22

  4. Dense Core Mass Function global pressure confinement Starless cores embedded in Pipe Nebula Pressure equilibrium with the surrounding warm medium Similarity between CMF & IMF CMF as the provenance of IMF Similar mass function as IMF 4/22

  5. Microphysics of thermal instability Norman & Krutsov Two phase medium balanced by pressure confinement Energy loss from hot medium through precipitation, not cooling Asymptotic thermal balance in the cold clouds due to external heating 5/22

  6. Phase transition during collisions Density enhancement and recombination (Murray) 6/22

  7. Growth of thermal instability Burkert Cooling vs sound crossing time From isobaric to isochoric cooling Power index of perturbation spectrum 7/22

  8. Growth limits to thermal instability Heating of the hot medium Conduction on small scales 8/22

  9. Sedimentation and heating Murray Buoyancy effect of pressure confined clouds: sedimentation, drag, fragmentation Energy branching ratio 9/22

  10. Coagulation equation • Dynamics of dense cores: • Coagualtion • Fragmentation • … • Thermal interaction • Gravity collapse & SF • Simulation results for • evolution in 2Myrs • (Huang et al 2011) + + + Starless CMF First stars born 10/22

  11. Bonner Ebert mass External pressure Pext Internal pressure Tint Critical Bonnor Ebert Mass gravity Pressure confined MBE ~ Tint2/Pext1/2 ？ Gravity confined Collapse 11/22

  12. Stellar Initial Mass Function orion nebula • Stellar Initial Mass Function • Importance • Kroupa IMF 12/22

  13. Photoionization of warm medium Gritschneder Mach 1.5 Mach 5 Mach 7 Mach 12.5

  14. Propagation of ionized region (qOph) Non spherical blister (Krumholz) where Is the Stromgren radius Three phases: molecular cores, confining atomic gas, and tenuous ionized HII. 14/22

  15. TriggeredInduced star formation • Sequential star formation First massive stars are born: uv radiation External temperature & pressure increased Bonnor Ebert Mass decreases Simultaneous core collapse Star burst 15/22

  16. Induced Star Formation:Evaporation Effect Star heats up its vicinity Dense cores evaporated?? Ionization V.S Recombination =>R~0.05pc<Rc Evaporation negligible 16/22

  17. Nonthermal velocities in fragments Rotational fragmentation Ang mom conservation =>3 magnitude dispersion Turbulence Bate et al 2010 17/22 Andrews et al 2010

  18. High angular momentum: BinarySystems Previous Bonnor Ebert Mass Binary fragmentation: M=M1+M2 M1<M2 Define mass ratio: q= M1/M 0<q<0.5 New Bonnor Ebert Mass Zhou et al 2012 Da Rio et al 2011 (Orion Nebula Cluster) 18/22

  19. Turbulence: angular momentum cancellation • Surface density evolution & spin flip • Disk may shrink to <0.1AU and be hot (1-2000K). CAIs may milt &re-condense after nebula resumes viscous diffusion & cools 19/22

  20. Supernova induced implosion Density Temperature

  21. The Formation Time of CAIs Re-melted CAIs Primitive CAIs From the spread among CAIs one can derive a relative condensation timescale of t≈20kyr From Pb-Pb measurements one can derive an absolute formation timescale of t≈4.6Gyr • The first generation of CAIs condensed 4.6 billion years ± 20 thousand years ago(e.g. Jacobsen et al, 2008, Earth and Planetary Science Letters 272, 353)

  22. Supernovae in dward galaxies (Fragile, Murray) Multiple massive stars Pregenitor HII regions Preferential ejection of Fe Preservation of H gas

  23. Summary & discussion • Multi-phase medium commonly co-coexist • Interaction between cores and pressure confining gas determines CMF • Cores mass function determines stellar IMF • Clusters formation is triggered by radiative and supernova feedback • Collective conduction between molecular cores, atomic, and ionized gas may regulate large scale cool stream flows 21/22

  24. Thank you Happy Birthday Avishai 生日快乐 Clumps ? 22/22

More Related