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San Diego Supercomputer Center, UCSD

Simulating the Cosmic History of Baryons Discoveries Using Advanced Computing Michael L. Norman, Physics Dept., UC San Diego. validation. San Diego Supercomputer Center, UCSD. Keck Observatory, HI. surveys. Baryogensis : GUT phase transition t~10(-12) s speculative.

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San Diego Supercomputer Center, UCSD

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  1. Simulating the Cosmic History of BaryonsDiscoveries Using Advanced ComputingMichael L. Norman, Physics Dept., UC San Diego validation San Diego Supercomputer Center, UCSD Keck Observatory, HI SciDAC 6-30-05 M. L. Norman

  2. surveys Baryogensis: GUT phase transition t~10(-12) s speculative Nucleosynthesis: formation of light nuclei t~1-100 s precision era (BBNS) Recombination: matter & radiation decouple t~380,000 yr precision era (CMB) Cosmic History of Baryons gravitational instability phase transitions Structure Formation: 50 Myr < t < 14 Gyr synthesis era linear perturbation theory nonlinear simulations SciDAC 6-30-05 M. L. Norman

  3. We are here SciDAC 6-30-05 M. L. Norman

  4. Cosmological N-body Simulation A. Evrard and the Virgo Consortium SciDAC 6-30-05 M. L. Norman

  5. SciDAC 6-30-05 M. L. Norman

  6. Multiscale Challenge Multiscale Challenge SciDAC 6-30-05 M. L. Norman

  7. Grand Challenges in Computational Hydrodynamic Cosmology • Formation and evolution of stellar systems on all scales and epochs • Chemical enrichment and reionization of intergalactic medium • Formation of massive black holes and nature of the quasar phenomenon • Cosmological constraints on nature of dark matter and dark energy SciDAC 6-30-05 M. L. Norman

  8. Outline • Cosmology’s Standard Model • Universe in a Box • History of Baryons: Discoveries using Advanced Computing • Exciting Opportunities Ahead • Cosmological limits on dark matter mass • Measuring dark energy equation of state SciDAC 6-30-05 M. L. Norman

  9. Cosmology’s Standard Model • Concordance model • H0=72+/-7 km/s/Mpc • expansion rate accelerating (q0<0) • flat universe (k=0) • dominated by dark matter and dark energy • baryons minor constituent Perlmutter (2003), Physics Today SciDAC 6-30-05 M. L. Norman

  10. Evidence for an Accelerating Universe S. Perlmutter, Physics Today (2003) SciDAC 6-30-05 M. L. Norman

  11. Cosmic Microwave BackgroundTemperature Fluctuations 380,000 yr ABB NASA WMAP DT/T ~ Dr/r ~ 10-4 SciDAC 6-30-05 M. L. Norman

  12. CMB Angular Power Spectrum SciDAC 6-30-05 M. L. Norman

  13. Mass-Energy Budget of the Universe (WMAP+SNe+XRC) WL SciDAC 6-30-05 M. L. Norman

  14. Universe in a Box

  15. The Universe is an IVP suitable for computation • Globally, the universe evolves according to the Friedmann equation cosmological constant Hubble parameter mass-energy density spacetime curvature scale factor a(t) SciDAC 6-30-05 M. L. Norman

  16. The Universe is an IVP... • Locally*, its contents obey: • Newton’s laws of gravitational N-body dynamics for stars and cold dark matter • Euler or MHD equations for baryonic gas/plasma • Atomic and molecular processes important for radiative cooling of gas and condensation to form stars and galaxies • Radiative transfer equation for photons  Numerical astrophysics on a cosmic scale (*scales << horizon scale ~ ct) SciDAC 6-30-05 M. L. Norman

  17. baryonic universe radiative transfer radiation background self-shielding photo-ionization photo-heating photo-evaporation ionizing flux absorption infall galaxies IGM feedback (energy, metals) SF-recipe multi-species hydrodynamics N-body dynamics cosmic expansion self-gravity dark matter dynamics SciDAC 6-30-05 M. L. Norman

  18. Cold Dark Matter • Dominant mass constituent: Wcdm~0.23 • Only interacts gravitationally with ordinary matter (baryons) • Candidates: WIMPs or axions • Collisionless dynamics governed by Vlasov-Poisson equation • Solved numerically using fast N-body methods SciDAC 6-30-05 M. L. Norman

  19. Gridding the Universe • Triply-periodic boundary conditions • Transformation to comoving coordinates x=r/a(t) But what about initial conditions? a(t1) a(t2) a(t3) SciDAC 6-30-05 M. L. Norman

  20. Matter Power Spectrum P(k) Concordance model http://www.hep.upenn.edu/~max SciDAC 6-30-05 M. L. Norman

  21. Gravitational Instability: Origin of Cosmic Structure very small fluctuations r C A <r> x B gravity amplifies fluctuations C A r <r> x B SciDAC 6-30-05 M. L. Norman

  22. Formation of the Cosmic Web: Sky Dome Rendering for DomeFest 2005 Michael Norman, Brian O’Shea, UCSD Donna Cox, Robert Patterson, Stuart Levy, UIUC Steve Cutchin, Amit Chourasia, SDSC

  23. Technical Details • Simulation (Enzo) • Dark matter, gravity, multispecies gas dynamics, photo-ionization and, radiative cooling • 1 billion cells, 1 billion particles • 512 cpu, NCSA TeraGrid cluster • Data • 512x512x512 arrays of density • 2000 timesteps • 1 Terabyte of data • Volume rendering • SDSC IBM DataStar SciDAC 6-30-05 M. L. Norman

  24. SciDAC 6-30-05 M. L. Norman

  25. Structured Adaptive Mesh Refinement (Berger and Colella 1989) SciDAC 6-30-05 M. L. Norman

  26. Cosmological Adaptive Mesh Refinement(Bryan & Norman 1997) • Spatial dynamic range unlimited in principle • Today: • L/D = 104 in statistical volumes • L/D =1010 single objects of interest • Petascale: • L/D =106 in statistical volumes SciDAC 6-30-05 M. L. Norman

  27. http://cosmos.ucsd.edu/enzo SciDAC 6-30-05 M. L. Norman

  28. Enzo Implementation Details • Multi-scale in space and time • Arbitrary # levels of refinement • Arbitrary # grids per level • Portable, MPI-parallel, C++/C/F77 hybrid • Nonlocal dynamic load balancing • Ported to IA64, SGI Altix, IBM SP, BG/L, your mother’s Linux cluster, ….. SciDAC 6-30-05 M. L. Norman

  29. SciDAC 6-30-05 M. L. Norman

  30. Galaxy Formation and Large Scale Structure • Technical details • 2563 base grid • >32,000 grid patches @ 8 levels of refinement • 110,000 cpu-hrs on 128 cpu Origin2000 • 0.5 TB of data • Run at NCSA in 1999 Science credit: M. Norman, G. Bryan, B. O’Shea Image credit: D. Cox et al.

  31. Computational Discoveriesusing Advanced Computing First baryonic condensations SciDAC 6-30-05 M. L. Norman

  32. “Bottom-Up” Galaxy Formation • large galaxies form from mergers of smaller galaxies • where does this begin? • What are the first objects to form? Lacey & Cole (1993) SciDAC 6-30-05 M. L. Norman

  33. First objects: a well-posed problem • Initial conditions specified: Wi, P(k) • Macroscopic dynamics understood • Microphysics of primordial gas known • Have 3D solution-adaptive algorithms • Have adequate computer power February 2003 SciDAC 6-30-05 M. L. Norman

  34. Formation 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 SciDAC 6-30-05 M. L. Norman

  35. Birth and Death of the First Star in the Universe Science credit: T. Abel, G. Bryan, M. Norman Movie credit: R. Kaehler & T. Abel SciDAC 6-30-05 M. L. Norman

  36. Impact of the first stars • the first stars in the universe began forming around 50 million years after the big bang • they were exceptionally massive and bright, bringing an earlier end to the cosmic “dark ages” than previously thought • when they exploded as supernovae they seeded the universe with heavy elements essential for planets and life • they kick-started the cosmogonic sequence which eventually formed galaxies, clusters and superclusters SciDAC 6-30-05 M. L. Norman

  37. Computational Discoveriesusing Advanced Computing structure of intergalactic medium SciDAC 6-30-05 M. L. Norman

  38. The Intergalactic Medium Source: M. Murphy SciDAC 6-30-05 M. L. Norman

  39. Structure of the IGM quasar N=10243 L=54 Mpc/h Simulated HI absorption spectrum Earth Baryon Overdensity, z=3 SciDAC 6-30-05 M. L. Norman

  40. Matter Power Spectrum P(k) LCDM http://www.hep.upenn.edu/~max SciDAC 6-30-05 M. L. Norman

  41. Computational Discoveriesusing Advanced Computing whereabouts of missing baryons SciDAC 6-30-05 M. L. Norman

  42. Missing Baryons at z=0 • Galaxies in local universe account for only 10% of baryons we know exist due to three independent measurements, which all agree to 2s • Big bang nucleosynthesis • CMB anisotropies • IGM absorption at high redshift • Where are the baryons now? SciDAC 6-30-05 M. L. Norman

  43. Whereabouts of the missing baryons: Warm-Hot intergalactic gas warm-hot gas “galaxies” Cen & Ostriker (1998) N=5123 SciDAC 6-30-05 M. L. Norman

  44. Exciting Opportunities Ahead(require Terascale and beyond) • Predicting properties of first galaxies • Understanding quasar-galaxy connection • Self-consistent simulation of the reionization era • Cosmological limits on dark matter mass • Measuring the dark energy equation of state SciDAC 6-30-05 M. L. Norman

  45. Effect of DM particle mass on first objects: critical threshold 25 keV 10 keV O’Shea & Norman (2005) SciDAC 6-30-05 M. L. Norman

  46. Measuring Dark Energy EOS • Principal goal of NASA/DOE JDEM mission • Approach: precision measurements of expansion history of the universe using Type Ia SN standardizable candles • Complimentary approach: redshift distribution of galaxy clusters SciDAC 6-30-05 M. L. Norman

  47. Evrard et al. Single, 10243 P3M L/D=104 Dark matter only Our plan Multiple, 5123 AMR Optimal tiling of lightcone L/D=105 Dark matter + gas 0 -1 -2 -3 -4 -5 Lightcone Simulation(A. Evrard et al. 2003) ct (Gyr) SciDAC 6-30-05 M. L. Norman

  48. Cosmic Simulator • A software facility for physical cosmology • A new collaboration between LLNL and UCSD • Scientific data management focus • Simulations: LLNL Thunder, BG/L • Data management: SDSC SRB • Public archive @ UCSD • Science driver: • LSST (Large Synoptic Survey Telescope) SciDAC 6-30-05 M. L. Norman

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