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Computing the Formation, Evolution, and Fate of our Hierarchical Universe

Computing the Formation, Evolution, and Fate of our Hierarchical Universe. Mike Norman Laboratory for Computational Astrophysics Physics Department and CASS UC San Diego. The Universe Exhibits a Hierarchy of Structures. The Universe Exhibits a Hierarchy of Structures. galaxy

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Computing the Formation, Evolution, and Fate of our Hierarchical Universe

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  1. Computing the Formation, Evolution, and Fate of our Hierarchical Universe Mike Norman Laboratory for Computational Astrophysics Physics Department and CASS UC San Diego

  2. The Universe Exhibits a Hierarchy of Structures The Universe Exhibits a Hierarchy of Structures galaxy superclusters dwarf galaxies galaxy groups galaxy superclusters dwarf galaxies galaxy groups star clusters star clusters galaxy clusters galaxies 109 100 101 102 103 104 105 106 107 108 galaxy clusters galaxies Light years 109 100 101 102 103 104 105 106 107 108 Light years

  3. The Cosmic Web 2dF Galaxy Redshift Survey

  4. Our universe then and now Recombination (~300,000 yr) dr/<r> ~ 10-5 Cosmic Background Explorer (NASA) Present (~13x109 yr) dr/<r> ~ 106

  5. History of the Universe phase transitions gravitational instability Hubble Deep Field Nucleosynthesis Recombination COBE, BOOMERANG, MAP linear perturbation theory nonlinear simulations

  6. Gravitational Instability: Origin of Cosmic Structure very small fluctuations r C A <r> x B gravity amplifies fluctuations C A r <r> x B

  7. Gravitational Instability in an Expanding Universe absolute comoving

  8. Gravitational Instability in 3-D: Origin of the “Cosmic Web” galaxies 500 million light years

  9. Gridding the Universe • Triply-periodic boundary conditions • Transformation to comoving coordinates x=r/a(t) a(t1) a(t2) a(t3)

  10. The Universe is an IVP suitable for computation • Globally, the universe evolves according to the Friedmann equation Hubble parameter mass-energy density spacetime curvature scale factor a(t)

  11. Concordance Model Bahcall, Ostriker, Perlmutter & Steinhardt (1999)

  12. The Universe is an IVP... • Locally, its contents obey: • Newton’s laws of gravitational N-body dynamics for stars and collisionless dark matter • Euler or MHD equations for baryonic gas/plasma • Atomic, molecular, and radiative processes important for the condensation of stars and galaxies from diffuse gas

  13. Main Loop of Hydrodynamic Cosmology Code Enzo Scale factor a(t) gas dynamics Gravity solver species solver heating & cooling Hydro solver star formation & feedback N-body solver radiative transfer New timestep

  14. Multiscale Challenge dynamic range requirement: > 104 spatial > 109 mass

  15. Multilevel Adaptive Grid Hierarchy level 4

  16. Adaptive Mesh Refinement Simulation of Galaxy FormationNorman, O’Shea & Bryan (2001)

  17. Adaptive Mesh Refinement Simulation of Galaxy Formation

  18. Initial Conditions Cosmic microwave background anisotropies Large scale distribution of galaxies

  19. Computational Discoveriesusing Hydrodynamic Cosmological Simulations Recombination Structure of intergalactic medium Whereabouts of missing baryons Nature of first stars

  20. Nature of First StarsAdaptive Mesh Refinement SimulationAbel, Bryan & Norman (2001) 1 x 10 x 100 x 1000 x Cosmic scales 104 x 105 x 107 x 106 x Solar system scales

  21. Structure of IGM: Physical Origin of the Lyman Alpha Forest • intergalactic medium exhibits cosmic web structure at high z • models explain observed hydrogen absorption spectra 5 Mpc/h N=1283 N=1283 Cen, Ostriker et al. (1994) Zhang, Anninos, Norman (1995)

  22. Whereabouts of the missing baryons: Warm-Hot IGM warm-hot gas “galaxies” Cen & Ostriker (1998) N=5123

  23. Challenges and Opportunities in Computational Cosmology • Formation and evolution of stellar systems on all scales and epochs • Chemical enrichment and reionization of IGM • Formation of massive black holes and nature of the quasar phenomenon • Cosmological constraints on nature of dark matter and dark energy

  24. Challenges and Opportunities Galaxy formation & LSS Recombination Massive black holes & quasar phenomenon Pre-galactic objects Cosmic reionization

  25. Pre-galactic Structures: The Universe at 100 million yrs Dark matter density Jena, Norman & Bryan (2001) 6 kpc

  26. Epoch of reionization seen? Transmitted flux vs. z Becker et al. (2001) SDSS Collaboration

  27. Reionization of IGM by First Galaxies Razoumov et al. (2001)

  28. Epoch of reionization sensitive to population of early galaxies Razoumov et al. (2001)

  29. Site Resources Site Resources 26 HPSS HPSS 4 24 External Networks External Networks 8 5 Caltech Argonne External Networks External Networks NCSA/PACI 8 TF 240 TB SDSC 4.1 TF 225 TB Site Resources Site Resources HPSS UniTree NSF PACI 13.6 TF Linux TeraGrid

  30. Impact of Terascale Facilities • More physical realism to needed to engage observables • Larger survey volumes for better statistics • Multi-scale resolution wherever needed • Automated parameter space searches • Formation of simulation of archives • Ability to engage massive observational surveys (SDSS, 2MASS, 2dFGRS,…)

  31. Problems only addressable by computational means • nature and consequences of first stars • structure formation prior to reionization (pre-galactic evolution) • formation of massive black holes • supernova/GRB mechanisms • origin of r-process elements

  32. Most Promising Paths (Organization and Funding) • Funding for develoment and evolution of community application software, including user training • More grand challenge teams, esp. synthesis of theory and observation

  33. Partnerships with Related Fields • Data grid technologies (CS) • Multiscale algorithms (AM) • Cosmological contraints on nature of dark matter and dark energy (AST)

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