解决原星系的形成。I.男性化
Resolving the Formation of Protogalaxies. I. Virialization
摘要：
星系形成的暗物质晕的层次结构。利用宇宙学三维自适应网格加密模拟，我们详细探讨了和谐宇宙学中重子的维里化，包括光学薄的原始气体冷却。我们关注维里温度为10^4 K的早期原星系及其祖先。没有冷却，维里加热发生在冲击接近维里半径的材料下降从空隙。致密细丝中的物质渗透得更深，约为半径的一半。随着冷却，维里激波位置收缩，细丝也达到维里半径三分之一的尺度。在绝热模拟中发现的原星系的温度从中心下降了2倍，并显示出平坦的熵核。在冷却晕中，气体通过其湍流速度与暗物质势达到维里平衡。我们观察到湍流马赫数从1到3的冷却情况。这种湍流是由大规模合并驱动的，有趣的是，即使在没有任何反馈过程的情况下，这些早期星系的中心仍然保持超音速。的维里定理被示出，以大约持有超过3个数量级的长度尺度的湍流压力占主导地位的热能。湍流的速度分布是麦克斯韦和到目前为止占主导地位的小旋转速度与星系的总角动量。分解的速度场使用柯西-斯托克斯定理，我们表明，大量的涡量存在于周围的冲击，甚至在这些对象的中心。
英文摘要：
(Abridged) Galaxies form in hierarchically assembling dark matter halos. With cosmological three dimensional adaptive mesh refinement simulations, we explore in detail the virialization of baryons in the concordance cosmology, including optically thin primordial gas cooling. We focus on early protogalaxies with virial temperatures of 10^4 K and their progenitors. Without cooling, virial heating occurs in shocks close to the virial radius for material falling in from voids. Material in dense filaments penetrates deeper to about half that radius. With cooling the virial shock position shrinks and also the filaments reach scales as small as a third the virial radius. The temperatures in protogalaxies found in adiabatic simulations decrease by a factor of two from the center and show flat entropy cores. In cooling halos the gas reaches virial equilibrium with the dark matter potential through its turbulent velocities. We observe turbulent Mach numbers ranging from one to three in the cooling cases. This turbulence is driven by the large scale merging and interestingly remains supersonic in the centers of these early galaxies even in the absence of any feedback processes. The virial theorem is shown to approximately hold over 3 orders of magnitude in length scale with the turbulent pressure prevailing over the thermal energy. The turbulent velocity distributions are Maxwellian and by far dominate the small rotation velocities associated with the total angular momentum of the galaxies. Decomposing the velocity field using the Cauchy-Stokes theorem, we show that ample amounts of vorticity are present around shocks even at the very centers of these objects.
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