高红移Ly $α$透射通量涨落的对数泊松非高斯性
Log-Poisson Non-Gaussianity of Ly$α$ Transmitted Flux Fluctuations at High Redshift
摘要：
利用类星体吸收谱的Ly $α$透射通量和对和谐$Λ$ CDM宇宙的宇宙学流体动力学模拟，研究了红移$z\sim 5 - 6$处IGM的非高斯特性。我们表明，中性氢质量密度场和Ly $α$传输通量波动具有所有的非高斯特性预测的对数泊松层次，这只取决于两个无量纲参数$β$和$γ$，分别描述，的不稳定性和奇异性的随机场。我们发现流体动力学模拟样本可以很好地再现类星体从$z=4.9$到$z=6.3$的Ly $α$透射通量的非高斯性。虽然在$5 - 6$的红移范围内，Gunn-Peterson光学厚度及其方差发生了显著的变化，但$β$测量的双折射率在此范围内几乎与红移无关。更有趣的是，发现类星体吸收谱在物理尺度$0.1-1$ h $^{-1}$ Mpc上的红移$5 - 6$与在物理尺度$1-10$ h $^{-1}$ Mpc上的红移$2 - 4$基本相同.考虑到Jeans长度在$z\sim 5$处小于0.1 h $^{-1}$ Mpc，在$z\sim 2$处小于0.1 h $^{-1}$ Mpc，这些结果意味着宇宙重子流体在高、低红移下的非线性演化将导致类似于充分发展的湍流状态.在所考虑的红移范围内，均匀的紫外背景可以解释类星体光谱高红移数据的对数泊松高阶行为。在考虑非均匀背景的情况下，我们还研究了对数泊松非高斯性。通过几种简化的非均匀背景模型，我们发现非均匀背景对对数泊松非高斯性的影响不大于1-sigma。
英文摘要：
We investigate the non-Gaussian features of the IGM at redshift $z\sim 5 - 6$ using Ly$α$ transmitted flux of quasar absorption spectra and cosmological hydrodynamic simulation of the concordance $Λ$CDM universe. We show that the neutral hydrogen mass density field and Ly$α$ transmitted flux fluctuations possess all the non-Gaussian features predicted by the log-Poisson hierarchy, which depends only on two dimensionless parameters $β$ and $γ$, describing, respectively, the intermittence and singularity of the random fields. We find that the non-Gaussianity of the Ly$α$ transmitted flux of quasars from $z=4.9$ to $z=6.3$ can be well reconstructed by the hydrodynamical simulation samples. Although the Gunn-Peterson optical depth and its variance underwent a significant evolution in the redshift range of $5 - 6$, the intermittency measured by $β$ is almost redshift-independent in this range. More interesting, the intermittency of quasar's absorption spectra on physical scales $0.1-1$ h$^{-1}$Mpc in redshift $5 - 6$ are found to be about the same as that on physical scales $1-10$ h$^{-1}$Mpc at redshifts $2 - 4$. Considering the Jeans length is less than 0.1 h$^{-1}$Mpc at $z\sim 5$, and $1$ h$^{-1}$Mpc at $z\sim 2$, these results imply that the nonlinear evolution in high and low redshifts will lead the cosmic baryon fluid to a state similar to fully developed turbulence. The log-Poisson high order behavior of current high redshift data of quasar's spectrum can be explained by uniform UV background in the redshift range considered. We also studied the log-Poisson non-Gaussianity by considering inhomogeneous background. With several simplified models of inhomogeneous background, we found the effect of the inhomogeneous background on the log-Poisson non-Gaussianity is not larger than 1-sigma.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
