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首页> 外文期刊>The Astrophysical journal >THE PROBABILITY DISTRIBUTION FUNCTION OF LIGHT IN THE UNIVERSE: RESULTS FROM HYDRODYNAMIC SIMULATIONS
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THE PROBABILITY DISTRIBUTION FUNCTION OF LIGHT IN THE UNIVERSE: RESULTS FROM HYDRODYNAMIC SIMULATIONS

机译：光在宇宙中的概率分布函数：水动力模拟的结果

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摘要

While second and higher order correlations of the light distribution have received extensive study, the lowest order probability distribution function (PDF)―the probability that a unit volume of space will emit a given amount of light―has received very little attention. We estimate this function with the aid of hydrodynamic simulations of the ACDM model, finding it significantly different from the mass density PDF, and not simply related to it by linear bias or any of the other prescriptions commonly adopted. If the optical light PDF is, in reality, similar to what we find in the simulations, then some measures of Ω_m based on the mass-to-light ratio and the cosmic virial theorem will have significantly underestimated Ω_m. Basically, the problem is one of selection bias, with galaxy-forming regions being unrepresentative of the dark matter distribution in a way not described by linear bias. Knowledge of the optical PDF and the plausible assumption of a lognormal distribution for the matter PDF will allow one to correct for these selection biases. We find that this correction (which amounts to 20%-30%) brings the values of Ω_m estimated by using the mass-to-light ratio and the cosmic virial theorem to the range Ω_m = 0.2-0.3, in better agreement with the Wilkinson Microwave Anisotropy Probe result than the uncorrected estimates. In addition, the relation between mass and light PDFs gives us insight concerning the nature of the void phenomenon. In particular, our simulation indicates that 20% of mass is distributed in voids, which occupy 85% of volume in the universe.
机译：虽然光分布的二阶和高阶相关已得到广泛研究，但是最低阶概率分布函数（PDF）（单位体积的空间将发射给定量的光的概率）却很少受到关注。我们借助ACDM模型的流体动力学模拟来估算此函数，发现它与质量密度PDF显着不同，并且不只是通过线性偏差或其他任何常用处方与其简单关联。如果实际上，光学PDF与我们在仿真中发现的相似，则基于质光比和宇宙病毒定理的Ω_m度量将大大低估Ω_m。基本上，问题是选择偏见之一，星系形成区域无法以线性偏见描述的方式无法代表暗物质分布。了解光学PDF以及物质PDF的对数正态分布的合理假设将使人们能够校正这些选择偏差。我们发现此校正（总计20％-30％）使通过使用质光比和宇宙病毒定理估算的Ω_m值达到Ω_m= 0.2-0.3的范围，与威尔金森更好地吻合微波各向异性探测的结果比未校正的估计要多。此外，质量PDF与轻量PDF之间的关系使我们对空隙现象的性质有了深入的了解。特别地，我们的模拟表明，质量的20％分布在空隙中，空隙占据了宇宙体积的85％。

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