Computational Astrophysics: Building Planets

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Computational Astrophysics Building Planets
SHARCNET AGM 2003, Guelph2003

• James Wadsley

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Computational Astrophysics

• Numerical modeling of dynamics and evolution of
  astrophysical systems
• Physics Gravity, Hydrodynamics, Magnetic Fields,
  Radiative Transfer, Atomic Chemistry
• Tools N-body Solvers, Fluid Dynamics Methods,
  Adaptive Meshes

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Early Simulations
Interacting Galaxies Holmberg 1941
74 light bulbs and patience
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And then there was SHARCNET

• 270,000,000 particles
• 1.3 Billion Lightyear cube
• 13 Billion Years Real Time
• 11 CPU Years PARALLEL Computer Time
• 1 month on Idra Supercomputer (SHARCNET_at_McMaster)

Cosmic Microwave Background, Sunyaev-Zeldovich
Effect Wadsley, Bond, et al. 2002
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Ingenuity vs. Moores Law

• Algorithms
• O(N2) Direct N-body
• O(N log2 N) Tree
• O(N) Hydro

O(N2)
O(N log2 N)
Time Adaptivity
Lake 2001
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• N-body Solver (Tree Method) and Smoothed Particle
  Hydrodynamics
• Parallel, adaptive in space and time
• Physics Gravity, Hydrodynamics, Atomic Chemistry
  (Radiative Heating, Cooling)
• Subgrid Physics Star Formation, Supernova
  Feedback, Planetesimal Collisions

Wadsley, Stadel Quinn 2003
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Applications
Disk Galaxy Formation Governato, Mayer, Wadsley,
et al. 2003
Cosmic Microwave Background, Sunyaev-Zeldovich
Effect Wadsley, Bond, et al. 2002
Intracluster light Willman, Governato, Wadsley,
et al.
Tidal Stirring of Dwarf Galaxies Mayer et al.
2001
Gas Giant Planets Mayer, Quinn, Wadsley Stadel
2002
Galaxy Cluster X-ray-Temperature
Relation Borgani, Governato, Wadsley, et al.
2001,2002
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Planets The Solar System
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Extrasolar Planets Not like the Solar System
DETECTION -gt SAMPLE
Elliptical Orbits
Bigger than Jupiter

• Over 100 detected http//exoplanets.org

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Star Forming Regions
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Planet Formation Mechanisms1) Planetesimal
Accretion

• Dust grains/ices settle and agglomerate up to 1
  km size
• 1 km size bodies gravitationally focus, collide
  perturb each other Runaway Growth to embryo size
  (0.1 MEARTH )
• Embryos collide/merge slow process
• 100 Myr years for Jupiter (Lissauer 1993)
• 10 MEARTH objects can accrete gas
• Does Jupiter have a core this large? (Guillot et
  al. 1999)

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Planet Formation Mechanisms2) Dynamical
Instabilities

• Outer Solar System was cold
• Potentially unstable to gravitational
  fragmentation on dynamical (orbital) timescales
• Inner Solar System was hot
• Keep the Planetesimal mechanism

Temperature vs. Radius (from Boss 2001)
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Gas Giant Formation Simulation
Mayer, Quinn, Wadsley Stadel, SCIENCE, 2002