Universal galaxy properties and the mass of the dark matter particle from theory and observations: the power of the linear approximation
Universal galaxy properties and the mass of the dark matter particle from theory and observations: the power of the linear approximation
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来自理论和观测的普遍星系特性和暗物质粒子的质量：线性近似的幂
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发表时间：
2010
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通讯作者：
N. Sanchez
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作者：
H. Vega;P. Salucci;N. Sanchez
我们将观察到的星系特性（如核心密度和半径）与从暴胀结束至今的第一原理计算出的密度涨落的理论线性演化相结合。光环半径 r_0 是根据宇宙学参数计算的。理论密度分布 rho(r)/rho(0) 具有作为 r/r_0 函数的通用形状，可重现观测结果。我们表明，玻尔兹曼-弗拉索夫方程的线性近似对于非常大的星系是有效的，并且正确地提供了所有星系共有的通用量，如表面密度和密度剖面。通过将理论计算的表面密度与其观测值相匹配，我们得到（i）MD时代相空间密度的减小（ii）暗物质粒子的质量变为1到2 keV之间，解耦温度T_d变为高于100 GeV（iii）核心与尖点的区别：keV暗物质粒子产生核心密度剖面，而wimps（m \ sim 100 GeV，T_d \ sim 5 GeV）可产生尺寸约为 0.03 pc 的尖点轮廓。这些结果与粒子模型无关，并且与暗物质粒子的统计数据变化很小。在大星系（r_0 和 M_{gal} 大）的极限情况下，非通用星系量（需要包括合并和重子等非线性效应）以线性近似的方式再现，晕半径 r_0、星系质量 M_{gal}、晕中心密度 rho_{0} 和速度色散 sqrt{{\overline {v^2}}_{halo}} 的线性近似为一阶因子。这显示了线性近似方案的威力：虽然它不能捕获结构形成的全部内容，但它正确地提供了通用量以及主要的非通用星系属性。
We combine observed properties of galaxies as the core density and radius with the theoretical linear evolution of density fluctuations computed from first principles since the end of inflation till today. The halo radius r_0 is computed in terms of cosmological parameters. The theoretical density profiles rho(r)/rho(0) have an universal shape as a function of r/r_0 which reproduces the observations. We show that the linear approximation to the Boltzmann-Vlasov equation is valid for very large galaxies and correctly provides universal quantities which are common to all galaxies, as the surface density and density profile. By matching the theoretically computed surface density to its observed value we obtain (i) the decreasing of the phase-space density during the MD era (ii) the mass of the dark matter particle which turns to be between 1 and 2 keV and the decoupling temperature T_d which turns to be above 100 GeV (iii) the core vs. cusp discrimination: keV dark matter particles produce cored density profiles while wimps (m \sim 100 GeV, T_d \sim 5 GeV) produce cusped profiles at scales about 0.03 pc. These results are independent of the particle model and vary very little with the statistics of the dark matter particle. Non-universal galaxy quantities (which need to include non-linear effects as mergers and baryons) are reproduced in the linear approximation up to a factor of order one for the halo radius r_0, galaxy mass M_{gal}, halo central density rho_{0} and velocity dispersion sqrt{{\overline {v^2}}_{halo}} in the limiting case of large galaxies (both r_0 and M_{gal} large). This shows the power of the linear approximation scheme: although it cannot capture the whole content of the structure formation, it correctly provides universal quantities which as well as the main non-universal galaxy properties.