multiphase medium in molecular clouds
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
Cosmological Streaming: Inflows & Outflows Jerusalem, Dec 15th, 2011
22 slides
Multiphase medium in molecular clouds
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Region of star formation - M16T. A. Rector & B. A. Wolpa, NOAO, AURA
McCaughrean & Andersen 2002, A&A, 389, 513
Molecular cloud: Pipe Nebula
Starless cores embedded in Pipe NebulaPressure equilibrium with the surrounding warm medium
Similarity between CMF & IMF
CMF as the provenance of IMF
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Lada et al 2008
Dense Core Mass Function
Starless cores embedded in Pipe NebulaPressure equilibrium with the surrounding warm medium
Similarity between CMF & IMF
CMF as the provenance of IMF
global pressure confinement
Similar mass function as IMF
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Microphysics of thermal instability
Norman &Krutsov
Two phase medium balanced by pressure confinementEnergy loss from hot medium through precipitation, not coolingAsymptotic thermal balance in the cold clouds due to external heating
5/22
Phase transition during collisions
Density enhancement and recombination (Murray) 6/22
Growth of thermal instabilityBurkert
Cooling vs sound crossing timeFrom isobaric to isochoric cooling
Power index of perturbation spectrum
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Growth limits to thermal instability
Conduction onsmall scales
Heating of the hot medium
8/22
Sedimentation and heating
Buoyancy effect of pressure confined clouds: sedimentation,drag, fragmentation
Energy branching ratio
Murray
9/22
Coagulation equation
Starless CMF
•Dynamics of dense cores:• Coagualtion
• Fragmentation
• …
• Thermal interaction• Gravity collapse & SF
•Simulation results for evolution in 2Myrs (Huang et al 2011) First stars born
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+ +
10/22
Bonner Ebert mass
External pressure Pext
Internal pressure Tint
gravity
core BEM M
core BEM M
Critical Bonnor Ebert Mass
Pressure confined
Gravity confined Collapse
?
11/22
MBE ~ Tint2/Pext
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Stellar Initial Mass Function
•Stellar Initial Mass Function
•Importance
•Kroupa IMF
1.3
2.35
,0.5 1.0,1.0 100
m Mdndm m M
orion nebula
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Photoionization of warm medium
Mach 1.5 Mach 5 Mach 7 Mach 12.5
Gritschneder
Propagation of ionized region (q Oph)
14/22
where Is the Stromgren radius
Non spherical blister (Krumholz)
Three phases: molecular cores, confining atomic gas, and tenuous ionized HII.
TriggeredInduced star formation
Sequential star formation
First massive stars are born: uv radiation
External temperature & pressure increased
Bonnor Ebert Mass decreases
Simultaneous core collapseStar burst
15/22
Induced Star Formation: Evaporation EffectStar heats up its vicinity Dense cores evaporated??
490 10 /Q photons s
0.1cR pc
0.83 13 342.56 10 /B T cm s
4 310 /Hn cm
=>R~0.05pc<RcEvaporation negligible
Ionization V.S Recombination
16/22
Nonthermal velocities in fragments
TurbulenceBate et al 2010
Rotational fragmentation
Ang mom conservation=>3 magnitude dispersion
Andrews et al 201017/22
High angular momentum: Binary Systems
New Bonnor Ebert Mass
Previous Bonnor Ebert Mass
Binary fragmentation:M=M1+M2M1<M2Define mass ratio:q= M1/M0<q<0.5
1.2 1.0
1.0
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Zhou et al 2012
Da Rio et al 2011 (Orion Nebula Cluster)
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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
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Supernova induced implosion
Density Temperature
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The Formation Time of CAIs
From the spread among CAIs one can derive a relative condensation timescale of t≈20kyrFrom 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)
Primitive CAIsRe-melted CAIs
Supernovae in dward galaxies (Fragile, Murray)Multiple massive starsPregenitor HII regionsPreferential ejection of FePreservation of H gas
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
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Thank you
Happy Birthday Avishai 生日快乐
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Clumps ?