以繪圖運算器處理多體問題: 模擬星系團碰撞之動力演化過程 以及小熊座矮橢圓星系中之動力化石

在這篇論文中我們主要探討暗物質暈的密度分布。藉由 NFW 分布曲線中的兩個變數,集中量和暈的質量,我們量測不同初始條件碰撞出來的暗物質暈的大小。集中量是暈和核心的半徑比。我們利用 GPU 的平行計算來進行模擬,如此可以比 CPU 的模擬快 300 倍的時間,而模擬的過程只考慮重力作用。我們利用不同的相對速度來碰撞暗物質暈。結果發現,當暗物質暈靠引力互相靠近而合併時,集中量平均會上升 8%。如果我們利用更快的相對速度進行碰撞,當動能提升 30% 時,暗物質暈的質量會流失 8%,但集中量卻會下降 3%,我們可以想像成過大的碰撞速度會破壞系統的核心,導致集中量沒有繼續增大。另外,我們利用模擬來解釋小熊座矮星系中星團的運行軌道,利用 ψDM,我們提供了一個平緩的核心密度,如此可以提供一個讓星團自由在其中運動的環境。而我們推測星團運行的軌道條件是,軌道應近似平行天球平面,可以有些微的徑向的速度,1km/s,而在天球上移動的最大速度則不可能超過 6km/s,以不超過暈的變界為條件。

關鍵字

冷暗物質；碰撞；集中量；小熊座矮星系；波色子暗物質

並列摘要

In this paper, we discuss the density distribution of DM halo. We want to understand that if the core size of the dark matter halo will change with different initial conditions of merging. We use NFW model with two param- eters to describe the DM halo, and these two parameters are concentration and the mass of the total halo. Concentration is the ratio between the size of DM halo and the core. In order to speed up the computing time, our lab use the GPU parallel computing process to simulate, thus it is 300 times faster than CPU code( [1]Chen 2007). The merging simulation is only consider the grav- itational interaction. We let the halos merge to others with different relative velocities and also the free falling case. The result shows that when we let the DM halos free fall to each other, the concentration of the new DM halo will increase 8%. On the other hand, if the relative kinetic energy increase 30%, the total mass of the new halo will decrease 8% and the concentration also decrease 5 On the other hand, we try to simulate the star clump underlie in the Ursa Minor dwarf spheroidal. We try to use our BEC dark matter, ψDM, to explain the possible orbits of the clump,which are all on the sky surface or with a small radius velocity 1km/s. We also give the upper limit of velocity of the clump that the halo can not move faster than 6km/s on the sky surface.

並列關鍵字

Cold Dark Matter ； Merging ； Concentration ； Ursa Minor Dwarf galaxy ； Bosonic Dark Matter

參考文獻

[2] Hsi-Yu Schive, Tzihong Chiueh, and Tom Broadhurst. Cosmi structure as the quan- tum interference of a coherent dark wave. Nature, 10:496--499, Jul. 2014.

[3] G. R. Blumenthal. Formation of galaxies and large-scale structure with cold dark matter. Nature, 311:517--525, Oct. 1984.

[4] Abraham Loeb and Matias Zaldarriaga. Small-scale power spectrum of cold dark matter. Physical Review D, 71, May 2005.

[6] J. Dunkley, D. N. Spergel, E. Komatsu, G. Hinshaw, and D. Larson. Five-year wilkinson microwave anisotropy probe (wmap) observations: Bayesian estimation of cosmic microwave background polarization maps. The Astrophysical Journal, 701:1804--1813, 2009.

[7] Andrey V. Kravtsov, Alexey Vikhlinin, and Daisuke Nagai. A new robust low- scatter x-ray mass indicator for clusters of galaxies. The Astrophysical Journal, 650:128--136, 10 2006.

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以繪圖運算器處理多體問題: 模擬星系團碰撞之動力演化過程以及小熊座矮橢圓星系中之動力化石

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