Tomoaki Ishiyama

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In this paper, we describe the implementation and performance of GreeM, a massively parallel TreePM code for large-scale cosmological N-body simulations. GreeM uses the recursive multi-section algorithm for domain decomposition. The size of the domains are adjusted so that the total calculation time of the force become the same on all processes. The loss of(More)
We have simulated, for the first time, the long term evolution of the Milky Way Galaxy using 51 billion particles on the Swiss Piz Daint supercomputer with our N-body gravitational tree-code Bonsai. Herein, we describe the scientific motivation and numerical algorithms. The Milky Way model was simulated for 6 billion years, during which the bar structure(More)
As an entry for the 2012 Gordon-Bell performance prize, we report performance results of astrophysical <i>N</i>-body simulations of one trillion particles performed on the full system of K computer. This is the first gravitational trillion-body simulation in the world. We describe the scientific motivation, the numerical algorithm, the parallelization(More)
As an entry for the 2012 Gordon-Bell performance prize, we report performance results of astrophysical N -body simulations of one trillion particles performed on the full system of K computer. This is the first gravitational trillion-body simulation in the world. We describe the scientific motivation, the numerical algorithm, the parallelization strategy,(More)
We report on the performance of our cold-dark matter cosmological N -body simulation which was carried out concurrently using supercomputers across the globe. We ran simulations on 60 to 750 cores distributed over a variety of supercomputers in Amsterdam (the Netherlands, Europe), in Tokyo (Japan, Asia), Edinburgh (UK, Europe) and Espoo (Finland, Europe).(More)
We present the results of the “Cosmogrid” cosmological N -body simulation suites based on the concordance LCDM model. The Cosmogrid simulation was performed in a 30Mpc box with 20483 particles. The mass of each particle is 1.28× 10M!, which is sufficient to resolve ultra-faint dwarfs. We found that the halo mass function shows good agreement with the Sheth(More)
We have investigated effects of dust attenuation on quasar luminosity functions at z ∼ 2 using a semi-analytic galaxy formation model combined with a large cosmological N-body simulation. We estimate the dust attenuation of quasars self-consistently with that of galaxies by considering the dust in their host bulges. We find that the luminosity of the bright(More)
Citation: Shirakata H, Kawaguchi T, Okamoto T, Makiya R, Ishiyama T, Matsuoka Y, Nagashima M, Enoki M, Oogi T and Kobayashi MAR (2017) Theoretical Re-evaluations of Scaling Relations between SMBHs and Their Host Galaxies—1. Effect of Seed BH Mass. Front. Astron. Space Sci. 4:15. doi: 10.3389/fspas.2017.00015 Theoretical Re-evaluations of Scaling Relations(More)