有无残余速度时暗物质晕在功率谱阻尼尺度上的结构
On the Structure of Dark Matter Halos at the Damping Scale of the Power Spectrum with and without Relict Velocities
摘要：
我们报道了一系列高分辨率的宇宙学N体模拟，旨在探索暗物质晕的形成和性质的质量接近阻尼尺度的原始功率谱的密度波动。我们进一步研究的效果，除了一个随机组件，v_rms，到粒子速度场的结构上的晕。我们采用的基准模型的λ温暖的暗物质宇宙学与非热无菌中微子质量为0.5千电子伏。过滤质量则对应于M_f = 2.6x10^12 M_sun/h。用几百万个粒子模拟了质量接近M_f的晕。结果表明，一方面，这些晕的内密度斜率（在半径<~0.02维里半径Rvir）系统地比对应于NFW拟合或CDM对应物的内密度斜率更陡。另一方面，整体密度分布（半径大于0.02Rvir）比NFW拟合更少弯曲和更少集中，外斜率小于-3。对于用v_rms进行的模拟，内晕密度轮廓在半径小于2-3 kpc/h（<~0.010-0.015Rvir）时显著平坦。在我们的模拟中没有检测到恒定密度的核心，除了一个晕，其扁平核心半径为~1 kpc/h。然而，如果用“核心”密度剖面来拟合晕剖面，则推断出的核心半径约为0.1-0.8 kpc/h，这与基于相空间约束和热引力坍缩动力学模型的理论预测大致一致。将v_rms减小3倍会导致纤芯半径适度减小，小于1.5倍。我们讨论了我们的结果扩展到几个方面，例如，在这个模型的阻尼尺度的冷DM微晕的结构。
英文摘要：
We report a series of high-resolution cosmological N-body simulations designed to explore the formation and properties of dark matter halos with masses close to the damping scale of the primordial power spectrum of density fluctuations. We further investigate the effect that the addition of a random component, v_rms, into the particle velocity field has on the structure of halos. We adopted as a fiducial model the Lambda Warm Dark Matter cosmology with a non-thermal sterile neutrino mass of 0.5 keV. The filtering mass corresponds then to M_f = 2.6x10^12 M_sun/h. Halos of masses close to M_f were simulated with several million of particles. The results show that, on one hand, the inner density slope of these halos (at radii <~0.02 the virial radius Rvir) is systematically steeper than the one corresponding to the NFW fit or to the CDM counterpart. On the other hand, the overall density profile (radii larger than 0.02Rvir) is less curved and less concentrated than the NFW fit, with an outer slope shallower than -3. For simulations with v_rms, the inner halo density profiles flatten significantly at radii smaller than 2-3 kpc/h (<~0.010-0.015Rvir). A constant density core is not detected in our simulations, with the exception of one halo for which the flat core radius is ~1 kpc/h. Nevertheless, if ``cored'' density profiles are used to fit the halo profiles, the inferred core radii are ~0.1-0.8 kpc/h, in rough agreement with theoretical predictions based on phase-space constrains, and on dynamical models of warm gravitational collapse. A reduction of v_rms by a factor of 3 produces a modest decrease in core radii, less than a factor of 1.5. We discuss the extension of our results into several contexts, for example, to the structure of the cold DM micro-halos at the damping scale of this model.
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