박창범 ( 고등과학원 ) & 김주한 ( 경희대학교 ), J. R. Gott (Princeton, USA), J. Dubinski (CITA, Canada) 한국계산과학공학회 창립학술대회 Cosmological N-Body Simulation of Cosmic Structure Formation

Simulation of Cosmic Structure Formation 1. Purpose of cosmological simulations 2. Structure 3. Requirements 4. Recent achievement

History of the Universe

우주 조망도 관측 가능한 시공간 대폭발 특이 면 빛 분리면 암흑시대 재이온화시기 현재 high-z 시대

Comparison between simulated universes with the real universe Cosmological model Initial linear density fluctuation Non-linear gravitational evolution Galaxy biasing Redshift space distortion Past light cone effects Survey characteristics Simulated sample of 'galaxies' The real universe Observed sample of galaxies Statistical test of adopted models Calibration of systematic effects Prediction of new phenomena

Simulation of Cosmic Structure Formation 1. Purpose 2. Structure of cosmological simulations 3. Requirements 4. Recent achievements

Execution of Cosmological Simulations 0-1. Simulation code N-body gravity code: PM, P3M, Tree, PM-Tree codes Hydro code: 1. particle - SPH 2. mesh (AMR) - ENZO, FLASH 0-2. Dynamic ranges Mass range: simulation particle, collapsed object, total # of particles Spatial range: simulation box size, force resolution

Structure of Cosmological Simulations 1. Initial conditions Cosmological model: power spectrum, high-order correlations Generation of initial conditions on a simulation mesh 2. Evolution & Intermediate analyses Snapshot, past-light cone, collapsed object data at predetermined epochs 3. Post analyses Merger tree construction Assignment of physical values to collapsed objects Comparison with observations

Growth of Structures from initial Density Fluctuations 13.7b 11.8b 7.7b t b =0

Simulation of Cosmic Structure Formation 1. Purpose 2. Structure 3. Requirements of cosmological simulations 4. Recent achievements

DreamReality 1Realty 2Reality 3 cosmic structures to simulate stars ~ horizonstars ~ galaxy*subgalactic objects ~ large-scale structure galaxy ~ cosmological scale Spatial scales to resolve 0.1pc~10 4 Mpc ~10 28 cm 0.1pc~100kpc ~10 23 cm few kpc ~ few 100Mpc ~10 27 cm few 10kpc~3000Mpc ~10 28 cm Spatial dynamic range : initial conditions / force resolution** / / 10 4 Dynamic range in mass (# of simulation particles) (memory~40TB) * Galaxy, a city of stars, is the building block of the universe ** Force resolution 10 times higher than the mean particle separation assumed Requirements for cosmological simulations

Simulation of Cosmic Structure Formation 1. Purpose 2. Structure 3. Requirements 4. Recent achievements

Dateparticlesscalesmachine ~1024 Mpc 0.275~5632 Mpc IBM SP3 at KISTI, 128 CPUs, 0.9 TB memory * ~6592 MpcSun Blade at KISTI, 1648 CPUs, 2.4TB memory planned** ~14000 Mpc40TB memory Major simulations of the KIAS astrophysical simulation group : LCDM model, PMTree N-body code, galaxy ~ cosmological scale * Horizon Run ** Horizon Run-II, a trillion particle simulation

( 김주한 & 박창범 2004) Simulation of bright galaxies and large-scale structure --> SDSS Main galaxy survey

T H E H O R I Z O N R U N Kim, Park, Gott & Dubinski (2009) Here Now Universe seen along the past light cone Decoupling Epoch Dark Ages The First ObjectsHI +  + He p + e - +  + He ReionizationEpoch Structure Formation & Evolution Acceleration (Dark Energy Dominated) Deceleration (Matter Dominated) Inflation SDSS Main

( 김주한, 박창범, Gott & Dubinski 2009) Simulation of very bright galaxies and large-scale structure; the 1st simulation out to the horizon --> SDSS-III Luminous Red Galaxy survey

Evolution of the number of simulation particles Horizon Run Millennium Run Horizon Run-II

Millennium Run Horizon Run Horizon Run-II Evolution of the spatial dynamic range box size resolution scale

Comparison between simulated universes with the real universe Cosmological model Initial linear density fluctuation Non-linear gravitational evolution Galaxy biasing Redshift space distortion Past light cone effects Survey characteristics Simulated sample of 'galaxies' The real universe Observed sample of galaxies Statistical test of adopted models Calibration of systematic effects Prediction of new phenomena

KSG-VAGC DR7 sample A tour of the real universe : SDSS galaxies

Final SDSS DR7 Main Galaxy Sample (2008) [Choi et al. 2009]

The Sloan Great Wall (Gott et al. 2005) The CfA Great Wall (Geller and Huchra 1989) The Cosmic Runner (Park et al. 2005)

SDSS2006 CfA1986

Voids (blue - 7% low), filaments/clusters (red - 7% high) => Sponge !! (Gott et al. 2008) SDSS2006

A mock survey of massive halos out to z=0.6 simulating the SDSS-III Luminosity Red Galaxy Survey that will finish in [the Horizon Run (Kim et al. 2009)]

Summary 1. The cosmological N-body gravity simulation is limited by memory, and hydrodynamics simulation is limited by both memory and speed. 2. In the near future a trillion particle N-body gravity simulation will be made for the first time. 3. The low-resolution cosmological simulation is now reaching the horizon scale. 4. The high-R cosmological simulations are increasing the box size, and the low-R simulations are increasing the force resolution toward smaller scales. 5. Cosmological simulations are indispensable for understanding the observed universe, guiding new surveys, and predicting new scientific findings.