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

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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

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Sedimentation and heating

Buoyancy effect of pressure confined clouds: sedimentation,drag, fragmentation

Energy branching ratio

Murray

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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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+ +

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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

？

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MBE ~ Tint2/Pext

1/2

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)

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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

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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

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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 ?