Research Areas      We are simulating large-scale structures of the universe using the GOTPM-II code, a significantly improved verion of the previous GOTPM. The research interests spam from the large-scale distributions of halos down to individual halos/subhalos to provide a testbed for the comparison with observations, for examples, the Sloan Digital Sky Survey and 2dF Galaxy Redshift survey. To identify dark matter halos from simulation particles, we developed a new halo finding method, the Physically Self Bound (PSB) which adopts the total energy and tidal boundary criteria to delineate halo/subhalo regions even in crowded environments.      Up to now, We have succeded the world-largest simulation at the time of 2009 ( Horizon-Run with 4120^3 particles) and many 2048^3 particle simulations with various simulation box sizes from super-Hubble scale to SDSS survey volume scale with a target for typical L* galaxies and LRGs. Using these simulation data we have compared the topology of mock and galaxy distributions and have analyzed the environmental effect on galaxy physical quantities. And many auxiliary small-size simulations have been frequently made for various specific purposes from time to time. If you want to get information of the specifics of the simulations we have done until now, please visit here . Research Facilities      QUEST: a Beowulf-type linux cluster with 64 nodes (256 cores of AMD CPUs) + 512 GB mem. + 20 TB disk      GPU: a GPU cluster with 24 nodes (96 Nvidia GPU C2050 cards) + 576 GB mem. + 10 TB disk      Myrinet: a Giga-bit device for data communication      OpenPBS: a parallel job management tool      Software: OpenMPI, MPICH, Portland Group Compiler, CUDA, and, IDL Research Members      Changbom Park, Professor      Juhan Kim, Research Professor      Jeong-Sun Hwang, Research Fellow      Do-Gyun Kim, Graduate Student Research Activities      Now all members in this research field at KIAS are currently working with the SDSS data. Professor Park is investigating the environmental effect on the galaxy properties, Mr. Do-Gyun Kim is working on the merging events and properties using close binary pairs of galaxies, and Prof. Kim is making mock galaxies and comparing their physical distributions with those of SDSS galaxies.      All members are currently involved in the development of the next-generation hydro code in the "Computational Astrophysics Group". Now, the individual time step is being implemented to the GOTPM-II and gas dynamics based on the SPH (smoothed Particle Hydrodynamics) will be included shortly. We are planning to simulate the heating and cooling functions calculated by the Cloudy90 packages. Also the star formation and supernova feedback algorithm will be added.      In 2011, we will simulate the galaxy formation and evolution in the cosmological context and study the luminosity distribution and morphological segragation of galaxies according to the environment, and the star formation history over the cosmic time scale.      The GPU version of the GOTPM-II is already developed and tested on the "gpu" cluster. The N-body calculation speed is about 130,000/second/GPU card which is about 2-3 times faster than the CPU cores. We are also planning to build a GPU version of the SPH-GOTPM code for a significant performance enhancement.      Also we are studying the feature of the Baryonic Acoustic Oscillation (BAO) imprinted on the power spectrum and two-point correlations to verify the cosmological model. We have run the Horizon-Run simulation mainly for this purpose and we have found the redshift evolution of the BAO in the matter and mock LRG correlations. Pictures & Movie Files      Fun pictures from the Horizon Run simulations Papers & Press Release      Preprints Archive      Press Release (Korean)

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