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

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

• Mike Norman
• Laboratory for Computational Astrophysics
• Physics Department and CASS
• UC San Diego

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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
100
101
102
103
104
105
106
107
108
109
galaxy clusters
galaxies
Light years
109
100
101
102
103
104
105
106
107
108
Light years
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The Cosmic Web
2dF Galaxy Redshift Survey
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Our universe then and now
Recombination (300,000 yr) dr/ltrgt 10-5
Cosmic Background Explorer (NASA)
Present (13x109 yr) dr/ltrgt 106
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History of the Universe
phase transitions
gravitational instability
Hubble Deep Field
Nucleosynthesis
Recombination
COBE, BOOMERANG, MAP
linear perturbation theory
nonlinear simulations
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Gravitational Instability Origin of Cosmic
Structure
very small fluctuations
r
C
A
ltrgt
x
B
gravity amplifies fluctuations
C
A
r
ltrgt
x
B
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Gravitational Instability in an Expanding Universe
absolute
comoving
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Gravitational Instability in 3-D Origin of the
Cosmic Web
galaxies
500 million light years
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Gridding the Universe

• Triply-periodic boundary conditions

• Transformation to comoving coordinates xr/a(t)

a(t1)
a(t2)
a(t3)
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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)
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Concordance Model
Bahcall, Ostriker, Perlmutter Steinhardt (1999)
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The Universe is an IVP...

• Locally, its contents obey
• Newtons 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

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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
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Multiscale Challenge
dynamic range requirement gt 104 spatial gt 109
mass
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Multilevel Adaptive Grid Hierarchy
level 4
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Adaptive Mesh Refinement Simulation of Galaxy
FormationNorman, OShea Bryan (2001)

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Adaptive Mesh Refinement Simulation of Galaxy
Formation
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Initial Conditions
Cosmic microwave background anisotropies
Large scale distribution of galaxies
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Computational Discoveriesusing Hydrodynamic
Cosmological Simulations
Recombination
Structure of intergalactic medium
Whereabouts of missing baryons
Nature of first stars
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Nature of First StarsAdaptive Mesh Refinement
SimulationAbel, Bryan Norman (2001)
1 x
10 x
100 x
1000 x
Cosmic scales
104 x
105 x
106 x
107 x
Solar system scales
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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
N1283
N1283
Cen, Ostriker et al. (1994) Zhang, Anninos,
Norman (1995)
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Whereabouts of the missing baryons Warm-Hot IGM
warm-hot gas
galaxies
Cen Ostriker (1998)
N5123
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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

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Challenges and Opportunities
Galaxy formation LSS
Recombination
Massive black holes quasar phenomenon
Pre-galactic objects
Cosmic reionization
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Pre-galactic Structures The Universe at 100
million yrs
Dark matter density
Jena, Norman Bryan (2001)
6 kpc
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Epoch of reionization seen?
Transmitted flux vs. z
Becker et al. (2001) SDSS Collaboration
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Reionization of IGM by First Galaxies
Razoumov et al. (2001)
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Epoch of reionization sensitive to population of
early galaxies
Razoumov et al. (2001)
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NSF PACI 13.6 TF Linux TeraGrid
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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,)

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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

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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

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Partnerships with Related Fields

• Data grid technologies (CS)
• Multiscale algorithms (AM)
• Cosmological contraints on nature of dark matter
  and dark energy (AST)