尖点/核心问题与二次降雨模型
The Cusp/Core problem and the Secondary Infall Model
摘要：
我们研究的尖点/核心问题，使用二次陷模型（SIM），考虑到有序和随机的角动量，动力学摩擦和重子绝热收缩的影响。该模型适用于星系尺度的结构（正常和矮螺旋星系）和星系团的规模。我们的分析表明，角动量和动力学摩擦能够，在星系尺度上，克服绝热收缩消除尖点的竞争效应。内晕密度剖面的斜率随晕质量的减小而减小，并与Burkert剖面很好地近似。为了获得NFW的配置文件，从我们的模型获得的配置文件开始，角动量和动力学摩擦的大小必须减少相对于模型本身预测的值。将Gentile等（2004）的四个LSB星系的自转曲线与本文模型得到的自转曲线进行了比较，得到了与观测数据的良好拟合。对$10^8-10^9 M_{\odot}$星系密度剖面的时间演化研究表明，经过一个瞬时的陡化过程后，由于绝热收缩，密度剖面逐渐变陡为$α\simeq 0$。在星系团尺度上，我们观察到暗物质密度分布的类似演化，但在这种情况下，密度分布斜率为$\simeq 10^{14} M_{\odot}$星系团的$α\simeq 0.6$。与暗物质不同的是，总质量分布显示出一个中心尖点，该中心尖点与NFW模型很好地拟合。
英文摘要：
We study the cusp/core problem using a secondary infall model (SIM) that takes into account the effect of ordered and random angular momentum, dynamical friction and baryons adiabatic contraction. The model is applied to structures on galactic scales (normal and dwarfs spiral galaxies) and on clusters of galaxies scales. Our analysis suggest that angular momentum and dynamical friction are able, on galactic scales, to overcome the competing effect of adiabatic contraction eliminating the cusp. The slope of density profile of inner haloes flattens with decreasing halo mass and the profile is well approximated by a Burkert's profile. In order to obtain the NFW profile, starting from the profiles obtained from our model, the magnitude of angular momentum and dynamical friction must be reduced with respect to the values predicted by the model itself. The rotation curves of four LSB galaxies from Gentile et al. (2004) are compared to the rotation curves obtained by the model in the present paper obtaining a good fit to the observational data. The time evolution of the density profile of a galaxy of $10^8-10^9 M_{\odot}$ shows that after a transient steepening, due to the adiabatic contraction, the density profile flattens to $α\simeq 0$. On cluster scales we observe a similar evolution of the dark matter density profile but in this case the density profile slope flattens to $α\simeq 0.6$ for a cluster of $\simeq 10^{14} M_{\odot}$. The total mass profile, differently from that of dark matter, shows a central cusp well fitted by a NFW model.
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