论文标题
由Baryon-Dark物质流速度引起的回离历史的大规模变化
Large-scale variation in reionization history caused by Baryon-dark matter streaming velocity
论文作者
论文摘要
在宇宙重组时,重子和暗物质之间存在超音速相对运动,这些运动源自早期宇宙中的重重声音振荡。由于相对速度迅速降低,因此人们认为这一运动对宇宙电离的后期有忽略不计。但是,最近的研究表明,与本地牛仔裤质量相比,气云的重组($ \ lyssim $ $ 10^8〜m_ \ odot $)可能会通过增加电离间层间培养基所需的紫外光子数量来影响电离历史。在此激励的情况下,我们进行了一系列辐射流动力模拟,以研究流动运动是否可以通过平滑块状的小规模结构并降低电离光子预算来产生局部电离历史记录的变化。我们发现,流速度可以增加$Δz_e$ $ \ sim $ $ $ 0.05 $ - $ - $ 0.5 $ 0.5 $的变化,取决于X射线预热的水平和电离源的时间演变。当星系的电离效率降低到以后的时间时,变化往往会更大。鉴于流动运动的长空间波动量表($ \ gtrsim 100 $ mpc),它可以帮助解释从类星体中观察到的ly $α$不透明度变化,并在抗离子化期间在galactic培养基的电离领域上留下大规模烙印。 X射线源进行的重新电源加热是另一个关键因素,可以抑制小规模的气体结块,并减少流动运动引入的$ Z_E $的变化。
At cosmic recombination, there was supersonic relative motion between baryons and dark matter, which originated from the baryonic acoustic oscillations in the early universe. This motion has been considered to have a negligible impact on the late stage of cosmic reionization because the relative velocity quickly decreases. However, recent studies have suggested that the recombination in gas clouds smaller than the local Jeans mass ($\lesssim$ $10^8~M_\odot$) can affect the reionization history by boosting the number of ultraviolet photons required for ionizing the intergalactic medium. Motivated by this, we performed a series of radiation-hydrodynamic simulations to investigate whether the streaming motion can generate variation in the local reionization history by smoothing out clumpy small-scale structures and lowering the ionizing photon budget. We found that the streaming velocity can add a variation of $Δz_e$ $\sim$ $0.05$ $-$ $0.5$ in the end-of-reionization redshift, depending on the level of X-ray preheating and the time evolution of ionizing sources. The variation tends to be larger when the ionizing efficiency of galaxies decreases toward later times. Given the long spatial fluctuation scales of the streaming motion ($\gtrsim 100$ Mpc), it can help to explain the Ly$α$ opacity variation observed from quasars and leave large-scale imprints on the ionization field of the intergalactic medium during the reionization. The pre-reionization heating by X-ray sources is another critical factor that can suppress small-scale gas clumping and can diminish the variation in $z_e$ introduced by the streaming motion.