Joachim Stadel

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In thki paper we describe PKDGRAV, a parallel hierarchical tree-structured code used to conduct cosmological simulations on shared-memory and message-passing multiprocessors. We explore performance traits of cosmological N-Body simulations on 32K to 1.3 million particles, running PKDGRAV on KSR-2 and Intel Paragon multiprocessors with up to 128 nodes. We(More)
We show that a universe dominated by cold dark matter fails to reproduce the rotation curves of dark matter dominated galaxies, one of the key problems that it was designed to resolve. We perform numerical simulations of the formation of dark matter halos, each containing ∼>10 particles and resolved to 0.003 times the virial radius, allowing an accurate(More)
The key features of the Gasoline code for parallel hydrodynamics with self-gravity are described. Gasoline is an extension of the efficient Pkdgrav parallel N-body code using smoothed particle hydrodynamics. Accuracy measurements, performance analysis and tests of the code are presented. Recent successful Gasoline applications are summarized. These cover a(More)
Leapfrog integration has been the method of choice in N-body simulations owing to its low computational cost for a symplectic integrator with second order accuracy. We introduce a new leapfrog integrator that allows for variable timesteps for each particle in large N-body simulations. Tests with single particles in fixed potentials show that it behaves as a(More)
We present a comprehensive set of convergence tests which explore the role of various numerical parameters on the equilibrium structure of a simulated dark matter halo. We report results obtained with two independent, state-of-the-art, multi-stepping, parallel N–body codes: PKDGRAV and GADGET. We find that convergent mass profiles can be obtained for(More)
We describe a new direct numerical method for simulating planetesimal dynamics in which N∼ 106 or more bodies can be evolved simultaneously in three spatial dimensions over hundreds of dynamical times. This represents several orders of magnitude improvement in resolution over previous studies. The advance is made possible through modification of a stable(More)
The evolution of gravitationally unstable protoplanetary gaseous disks has been studied with the use of three-dimensional smoothed particle hydrodynamics simulations with unprecedented resolution. We have considered disks with initial masses and temperature profiles consistent with those inferred for the protosolar nebula and for other protoplanetary disks.(More)
We investigate the mass profile of ΛCDM halos using a suite of numerical simulations spanning five decades in halo mass, from dwarf galaxies to rich galaxy clusters. These halos typically have a few million particles within the virial radius (r200), allowing robust mass profile estimates down to radii below 1% of r200. Our analysis confirms the proposal of(More)