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Outflow Feedback Regulated Massive Star Formation

Outflow Feedback Regulated Massive Star Formation. Zhi-Yun Li (Univ of Virginia). 3 pc. Collaborators: Peng Wang (Stanford) Tom Abel (Stanford) & Fumitaka Nakamura (Niigata). Stars form in turbulent, magnetized molecular clouds (Tan’s talk) Key ingredient in dense clumps

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Outflow Feedback Regulated Massive Star Formation

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  1. Outflow Feedback Regulated Massive Star Formation Zhi-Yun Li (Univ of Virginia) 3 pc Collaborators: Peng Wang (Stanford) Tom Abel (Stanford) & Fumitaka Nakamura (Niigata)

  2. Stars form in turbulent, magnetized • molecular clouds (Tan’s talk) • Key ingredient in dense clumps • of active cluster formation: • protostellar outflows Gutermuth et al. NGC 1333 Cluster-Forming Region by Spitzer • Outflows dynamically important? • (Norman & Silk 1980, McKee 1989, Shu et al. 1999) • ‹v›~MP/Mc ~SFE P • ~5km/s (SFE/0.2) (P/25km/s) • > 1-2km/s Sun et al. (2006)

  3. Stars form in turbulent, magnetized • molecular clouds • Key ingredient in dense clumps • of active cluster formation: • protostellar outflows Blue- & red-shifted molecular outflows NGC 1333 Cluster-Forming Region by Spitzer • How do outflows affect the • formation of stars in clusters, • particularlymassive stars? • A set of numerical experiments Sun et al. (2006)

  4. Setup of ENZO-based AMR-MHD simulations with sink particles(Wang, Li, Abel & Nakamura, ApJ, submitted) Box size: 2 pc - Spherical cloud with total mass = 1641 Msun and initial density profile: • Cs=0.265 km/s (T=20 K); • Initial turbulence has k^{-2} Burger’spower spectrum with M=9 • - Uniform magnetic field in z direction. Mass-to-flux ratio: overall: 1.4; central: 3.3. • Sink particle to model star formation- Protostellar outflow feedback. • Top grid 128^3, 4 levels of refinement • by 2, maximum resolution 200 AU. • Effective resolution 2048^3 ✓ ✓

  5. Massive stars form readily if unregulated by either magnetic fields or outflows • There are 5 massive stellar objects at the end of the simulation (t=3 central free fall times or ~0.6 Myr), with 61, 23, 10, 21,16, & 13 M • 137 stars with masses greater than 0.1 solar masses have formed

  6. Accretion history of the most massive object Model HD (only turbulence, no B, no outflow) MHD One global dynamical time

  7. Origin of high mass accretion rate t=1.5 t=3.0 Filament-fed rapid accretion (Banerjee et al. 06) Global collapse-driven rapid accretion

  8. Summary: Unregulated, Clump-Fed Massive Star Formation (from HD model) • Two phases of feeding:- Early phase: fed by formation and collapse of filament - Later phase: fed by global collapse • In both phases, mass is gathered mainly by an agent external to the stellar object --- not competitive accretion dominated by stars (if removed, another forms) • In our particular simulations, not from pre-existing or pre-assembled dense massive cores (continuously fed from relatively large scales) • Moderate magnetic fields do not change this picture qualitatively…

  9. Accretion history of the most massive object HD MHD (with turb & B, no outflow) WIND (w/ turb, B & outflow) Time (Myr) One global dynamical time

  10. Strong Regulation of Massive Star Formation by Outflows • Difference between • HD and WIND models • at t=3 (~0.6 Myr) • 5 massive stellar objects • for unregulated HD • 0 massive star at t=3 • for WIND model • Four massive stars at • end of WIND model HD (no B, no outflow) Accretion rate (1e-4 Msun/yr) HD WIND (both B & outflow) MHD (46, 12, 16, & 12 M)

  11. Outflow regulation of massive star formation at early times Disruption of dense filaments HD MHD HD (no B, no outflow) WIND (both B & outflow)

  12. Outflow regulation of massive star formation at late times Strongly regulated (subsonic) infall (WIND) Suppression of global collapse by outflows Sound speed Unregulated global (supersonic) collapse (HD) HD HD (no B, no outflow) WIND (both B & outflow) Average infall speed

  13. Total star formation rate Base HD Maximum free-fall rate = M/tff MHD 10% free-fall rate Wind

  14. Summary (Wang, Li, Abel & Nakamura 2009) • Two channels for rapid accretion to form • massive stars in our simulations: turbulent • compression & global collapse • Both channels regulated by outflows: • chopping up filaments & preventing • global collapse • Massive stars formed in our simulations are • Outflow-Regulated & Clump-Fed (ORCF) Low-mass cluster members can affect the formation of massive stars

  15. Backup slides • Core mass and stellar mass • Better view of outflows • Outflow movie

  16. Not from pre-existing, massive, 0.1pc-sized core Core, defined as region within 0.05 pc radius of the most massive object Low mass stars Massive object Mass (Msun) Core mass within 0.05pc of the most massive object Time [Myr]

  17. Outflow disruption of filaments

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