A natural symmetrization for the plummer potential

Saitoh, Takayuki R.; Makino, Junichiro

doi:10.1016/j.newast.2011.07.011

Cited by 10 publications

(4 citation statements)

References 32 publications

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“…I use a simulation code ASURA (Saitoh et al 2008, 2013, 8 in which a symmetric form of a Plummer softening kernel (Saitoh & Makino 2012), a parallel tree method with an computational accelerator GRAPE (GRAvity PipE, Makino 2004;Tanikawa et al 2013) and the second-order leap-frog integrator with individual timesteps are used. The number of stellar particles, 3 but for halo models different in rs and σ h .…”

Section: Settingsmentioning

confidence: 99%

Emergence of a stellar cusp by a dark matter cusp in a low-mass compact ultrafaint dwarf galaxy

Inoue

2017

Monthly Notices of the Royal Astronomical Society

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Recent observations have been discovering new ultra-faint dwarf galaxies as small as ∼ 20 pc in half-light radius and ∼ 3 km s −1 in line-of-sight velocity dispersion. In these galaxies, dynamical friction on a star against dark matter can be significant and alter their stellar density distribution. The effect can strongly depend on a central density profile of dark matter, i.e. cusp or core. In this study, I perform computations using a classical and a modern analytic formulae and N -body simulations to study how dynamical friction changes a stellar density profile and how different it is between a cuspy and a cored dark matter haloes. This study shows that, if a dark matter halo has a cusp, dynamical friction can cause shrivelling instability which results in emergence of a stellar cusp in the central region < ∼ 2 pc. On the other hand, if it has a constant-density core, dynamical friction is significantly weaker and does not generate a stellar cusp even if the galaxy has the same line-of-sight velocity dispersion. In such a compact and low-mass galaxy, since the shrivelling instability by dynamical friction is inevitable if it has a dark matter cusp, absence of a stellar cusp implies that the galaxy has a dark-matter core. I expect that this could be used to diagnose a dark matter density profile in these compact ultra-faint dwarf galaxies.

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Section: Settingsmentioning

confidence: 99%

Emergence of a stellar cusp by a dark matter cusp in a low-mass compact ultrafaint dwarf galaxy

Inoue

2017

Monthly Notices of the Royal Astronomical Society

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“…It is fairly easy to incorporate higher-order multipole expansion terms into our method, and it would be a natural extension to the present work. Another good application of the tree method on a GPU would be to simulations that adopt a symmetrized Plummer potential (Saitoh & Makino, 2010). We believe that our method is the best for implementing that proposal, and hence that we shall certainly obtain better accuracy and good performance in simulating galaxy evolution and formation with different mass resolutions.…”

Section: Discussionmentioning

confidence: 99%

Implementation of a parallel tree method on a GPU

Nakasato

2012

Journal of Computational Science

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The kd-tree is a fundamental tool in computer science. Among other applications, the application of kd-tree search (by the tree method) to the fast evaluation of particle interactions and neighbor search is highly important, since the computational complexity of these problems is reduced from O(N 2 ) for a brute force method to O(N log N) for the tree method, where N is the number of particles. In this paper, we present a parallel implementation of the tree method running on a graphics processing unit (GPU). We present a detailed description of how we have implemented the tree method on a Cypress GPU. An optimization that we found important is localized particle ordering to effectively utilize cache memory. We present a number of test results and performance measurements. Our results show that the execution of the tree traversal in a force calculation on a GPU is practical and efficient.

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“…The CO is modeled as a point mass which interacts only gravitationally with other particles. We set gravitational softening lengths to prevent numerical divergences during close approaches to √ 2ǫ, ǫ, and 0 for gas-gas particles, gas-CO, and CO-CO interactions, respectively [36].…”

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confidence: 99%

Compact Object Mergers Driven by Gas Fallback

2018

Self Cite

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Recently, several gravitational wave detections have shown evidence for compact object mergers. However, the astrophysical origin of merging binaries is not well understood. Stellar binaries are typically at much larger separations than what is needed for the binaries to merge due to gravitational wave emission, which leads to the so-called final AU problem. In this Letter we propose a new channel for mergers of compact object binaries which solves the final AU problem. We examine the binary evolution following gas expansion due to a weak failed supernova explosion, neutrino mass loss, core disturbance, or envelope instability. In such situations the binary is possibly hardened by ambient gas. We investigate the evolution of the binary system after a shock has propagated by performing smoothed particle hydrodynamics simulations. We find that significant binary hardening occurs when the gas mass bound to the binary exceeds that of the compact objects. This mechanism represents a new possibility for the pathway to mergers for gravitational wave events.

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A natural symmetrization for the plummer potential

Abstract: We propose a symmetrized form of the softened gravitational potential which is a natural extension of the Plummer potential. The gravitational potential at the position of particle i (x i

Cited by 10 publications

References 32 publications

Emergence of a stellar cusp by a dark matter cusp in a low-mass compact ultrafaint dwarf galaxy

Emergence of a stellar cusp by a dark matter cusp in a low-mass compact ultrafaint dwarf galaxy

Implementation of a parallel tree method on a GPU

Compact Object Mergers Driven by Gas Fallback

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