Simulating the 4% Universe Hydro-cosmology simulations and data - PowerPoint PPT Presentation

Simulating the 4% Universe Hydro-cosmology simulations and data analysis Michael L. Norman SDSC/UCSD

Lecture Plan • Lecture 1: Hydro-cosmology simulations of baryons in the Cosmic Web – Lyman alpha forest (LAF) – Baryon Acoustic Oscillation (BAO) • Lecture 2: Radiation hydro-cosmology simulations of Cosmic Renaissance – Epoch of Reionization (EOR) – First Galaxies 7/17/2012 ISSAC 2012, SDSC, San Diego USA 2

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1. First Stars 2. First Galaxies Cosmic Renaissance 3. Reionization 7/17/2012 ISSAC 2012, SDSC, San Diego USA 4

When did reionization complete? 7/17/2012 ISSAC 2012, SDSC, San Diego USA 5

Scientific Goals • Connect reionization to first galaxies through direct numerical simulations • Some Questions – How does reionization proceed? – Is the observed high-z galaxy population sufficient to reionize the Universe? – How is galaxy formation and the IGM modified by reionization? – How good are the analytic and semi-numerical models of reionization? 7/17/2012 ISSAC 2012, SDSC, San Diego USA 6

Three generations of cosmological reionization simulations 1. Local self-consistent • – (small boxes < 10 Mpc) – CRHD+SF+ionization+heating – e.g., Gnedin 2000, Razoumov et al. 2002 2. Global post-processing • – (large boxes > 100 Mpc) – N-body + RT – e.g., Iliev et al. 2006 • 3. Global self-consistent – (large boxes > 100 Mpc) – CRHD+SF+ionization+heating – Norman et al. 2012, in prep. 7/17/2012 ISSAC 2012, SDSC, San Diego USA 7

Post-processing Approach • Pioneered by Sokasian et al. (2003) and “perfected” by Iliev, Shapiro, et al. (2006+) • Recipe: – Perform high resolution N-body DM simulation in large volume (L>100 Mpc/h) – Assign ionizing flux to every halo by some prescription – Post-process snapshots of the density field, sampled onto a coarse grid, with a ray-tracing radiative transfer code, assuming baryons trace DM – Sources and gas clumping factor “coarse grained” on the mesh – No radiative feedback on source population or intergalactic gas 7/17/2012 ISSAC 2012, SDSC, San Diego USA 8

Post-processing Approach • Key insights – reionization proceeds from the “inside-out” (i.e., from overdense to underdense regions) – reionization is “rapid” ( ∆ z~2) • However – redshift of overlap is not predicted , but can be “dialed in” since it depends critically on assumed (M halo /L ion ) and f esc – minimum halo mass cutoff a free parameter 7/17/2012 ISSAC 2012, SDSC, San Diego USA 9

Self-Consistent Approach radiative transfer baryonic sector radiation background self-shielding photo-ionization photo-heating photo-evaporation ionizing absorption flux infall galaxies IGM feedback SF-recipe multi-species (energy, metals) N-body dynamics hydrodynamics dark matter cosmic expansion self-gravity dynamics 7/17/2012 ISSAC 2012, SDSC, San Diego USA 10

https://code.google.com/p/enzo 7/17/2012 ISSAC 2012, SDSC, San Diego USA 11

What does “direct simulation” mean? • All physical processes are simulated at the same mass and spatial resolution – DM, gas dynamics – parameterized star formation and feedbacks – radiation sources and transport – ionization/recombination/photoevaporation • Only subgrid model is SF, which is calibrated to observations (Bouwens et al.) • Advantage: sources and sinks of ionizing radiation and radiative feedback effects are simulated directly • Disadvantage: very costly to bridge scales; some still missing (minihalos) 7/17/2012 ISSAC 2012, SDSC, San Diego USA 12

Two Simulations Differing only in Volume Λ CDM, WMAP7 Run A Run B “¼ scale simulation” “Renaissance Simulation” 20 Mpc 80 Mpc 800 3 cells/particles 3200 3 cells/particles 64x volume Run A and Run B have identical mass and spatial resolution, physics, ICs, etc. 7/17/2012 ISSAC 2012, SDSC, San Diego USA 13

Mass and Spatial Resolution GOALS • HMF complete to ~10 8 M s to include dwarfs – Sets “minimal” mass and spatial resolution – M p = 5x10 5 M s – ∆ x=25 ckpc Run B • Simulate largest volume possible with available computer resources 7/17/2012 ISSAC 2012, SDSC, San Diego USA 14

Numerical Methods • We use Enzo V2.1 in non-AMR mode http://enzo.googlecode.com – 6 species fluid dynamics: PPM – Dark matter dynamics: Particle-Mesh – Gravity: FFTs • Radiation transport: implicit flux- limited diffusion, coupled to gas ionization and energy equation (Reynolds et al. 2009) Star formation & SN feedback: • modified Cen & Ostriker 92 with “distributed feedback” (Smith et al. 2011) – Calibrated to Bouwens et al. (2011) SFRD • UV radiative feedback: Pop II SED from Ricotti, Gnedin & Shull 2002 7/17/2012 ISSAC 2012, SDSC, San Diego USA 15

Tests of Radiation Solver Reynolds et al. (2009) • Correct I-front speeds are obtained even at low resolution due to implicit coupling of rad. transfer, ionization, and gas heating Shapiro & Giroux ‘87 analytic test problem 7/17/2012 ISSAC 2012, SDSC, San Diego USA 16

Results • Run A (1/4 scale simulation) – Ionizing photons per H atom – Adequacy of MHR estimate • Run B (Renaissance Simulation) – Role of large scale power – Suppression of star formation in low mass halos due to radiative feedback 7/17/2012 ISSAC 2012, SDSC, San Diego USA 17

ENZO radiation hydrodynamic cosmic reionization G. So, M. Norman, R. Harkness (UCSD), D. Reynolds (SMU) Redshift/time evolution of density and temperature 800 3 /20 Mpc/512 core density z=12.5 z=9.2 z=8 z=7 z=6 temperature t=362 Myr t=552 Myr t=664 Myr t=792 Myr t=969 Myr 7/17/2012 ISSAC 2012, SDSC, San Diego USA 18

ENZO radiation hydrodynamic cosmic reionization M. Norman, R. Harkness, G. So (UCSD), D. Reynolds (SMU) Redshift/time evolution of density and temperature 800 3 /20 Mpc/512 core density temperature 7/17/2012 ISSAC 2012, SDSC, San Diego USA 19

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Ionized Volume Fraction 7/17/2012 ISSAC 2012, SDSC, San Diego USA 21

Photons per H atom btw. 3.5-4.5 ionizing photons per H atom 7/17/2012 ISSAC 2012, SDSC, San Diego USA 22

Visualizing “Inside-Out” Reionization: Z-reion Cube • Every cell contains the redshift when it was first photo-ionized • yt script: – Loop over all redshift outputs (80) and test if f HII >0.9 – Uses nested parallel Z-reion objects to divide up the work on 256 cores – 56 sec on Gordon including IO 7/17/2012 ISSAC 2012, SDSC, San Diego USA 23

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Result 7/17/2012 ISSAC 2012, SDSC, San Diego USA 25

Effective of Large Scale Power slice 7/17/2012 ISSAC 2012, SDSC, San Diego USA 26

Effective of Large Scale Power slice 7/17/2012 ISSAC 2012, SDSC, San Diego USA 28

Effect of large scale power 7/17/2012 ISSAC 2012, SDSC, San Diego USA 29

HI going, going, gone…. Z=7 Z=6.5 Z=6.05 80 cMpc Large-scale neutral Projected HI fraction patches before overlap 7/17/2012 ISSAC 2012, SDSC, San Diego USA 30

Effect of large scale power 7/17/2012 ISSAC 2012, SDSC, San Diego USA 31

Where is the star formation happening? Z=7.3 7/17/2012 ISSAC 2012, SDSC, San Diego USA 32

Where is the star formation happening? Star formation strongly suppressed at M h < 5x10 9 M s 7/17/2012 ISSAC 2012, SDSC, San Diego USA 33

Is this a resolution effect? NO adiabatic hydro SF + SN feedback SF + SN feedback + radiative feedback 7/17/2012 ISSAC 2012, SDSC, San Diego USA 34

Is this a resolution effect? NO Ratio of Halo Gas Masses Depletion of baryons due to Depletion of SN feedback baryons due to radiative feedback 7/17/2012 ISSAC 2012, SDSC, San Diego USA 35

Visualizing Jeans Smoothing M. Norman, G. So, R. Harkness (UCSD), D. Reynolds (SMU) Density fields from RHD and non-RHD models Z=8 z=8, RHD z=8, HD Visualization by J. Insley (ANL) & R. Wagner (SDSC) 7/17/2012 ISSAC 2012, SDSC, San Diego USA 36

Visualizing Jeans Smoothing Normailzed density difference between RHD and non-RHD models Z=8 z=8, RHD z=8, HD Visualization by J. Insley (ANL) & R. Wagner (SDSC) 7/17/2012 ISSAC 2012, SDSC, San Diego USA 37

Visualizing Jeans Smoothing Normailzed density difference between RHD and non-RHD models Z=8 z=8, RHD z=8, HD radiative non-radiative no difference Visualization by J. Insley (ANL) & R. Wagner (SDSC) 7/17/2012 ISSAC 2012, SDSC, San Diego USA 38

ρ 2 radiative density dist. minus ρ 1 non-radiative density dist. red red normalized density difference ρ 2 - ρ 1 ρ 2 + ρ 1 yellow 7/17/2012 ISSAC 2012, SDSC, San Diego USA 39

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Jeans Smoothing 7/17/2012 ISSAC 2012, SDSC, San Diego USA 41

Effect on Dark Matter Power 7/17/2012 ISSAC 2012, SDSC, San Diego USA 42

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