炽热宇宙中的莱曼α森林
The Lyman-alpha forest in a blazar-heated Universe
摘要：
直到最近，人们才意识到耀变体的TeV辐射可以通过产生高能电子和正电子对来显著加热星系际介质（IGM），这反过来又激发了剧烈的等离子体不稳定性，导致对的动能的局部耗散。在这项工作中，我们使用宇宙流体动力学模拟的影响，这耀变体加热的莱曼α森林在红移z~2-3。我们发现，耀变体加热产生的IGM倒置的温度-密度关系，自然解决了许多问题，在以前的模拟森林，包括光加热。特别是，我们的模拟与耀变体加热同时再现观测到的有效光学深度和温度作为红移的函数，观测到的透射通量的概率分布函数，和观测到的通量功率谱，在整个红移范围2<z<3分析。此外，通过将莱曼-α森林分解成热加宽的各条线的总和，我们发现与观察到的线宽分布和中性氢柱密度丰度的下限一致。使用宇宙紫外线（UV）背景的最新限制，这种与观测结果的良好一致性不需要重新调整UV背景的幅度;过去经常使用的程序是匹配观测到的透射通量水平。我们还表明，我们的耀变体加热模型匹配的数据比标准模拟更好，即使这样的重新缩放是允许的。莱曼-α数据和基于最新宇宙学参数的模拟之间的这种一致性表明，blazar加热的包含消除了以前对来自莱曼-α测量和其他宇宙学数据的sigma_8的约束的紧张关系。[删节]
英文摘要：
It has been realised only recently that TeV emission from blazars can significantly heat the intergalactic medium (IGM) by pair-producing high-energy electrons and positrons, which in turn excite vigorous plasma instabilities, leading to a local dissipation of the pairs' kinetic energy. In this work, we use cosmological hydrodynamical simulations to model the impact of this blazar heating on the Lyman-alpha forest at redshifts z~2-3. We find that blazar heating produces an inverted temperature-density relation in the IGM and naturally resolves many of the problems present in previous simulations of the forest that included photoheating alone. In particular, our simulations with blazar heating simultaneously reproduce the observed effective optical depth and temperature as a function of redshift, the observed probability distribution functions of the transmitted flux, and the observed flux power spectra, over the full redshift range 2<z<3 analysed here. Additionally, by deblending the Lyman-alpha forest into a sum of thermally broadened individual lines, we find superb agreement with the observed lower cutoff of the line-width distribution and abundances of neutral hydrogen column densities. Using the most recent constraints on the cosmic ultraviolet (UV) background, this excellent agreement with observations does not require rescaling the amplitude of the UV background; a procedure that was routinely used in the past to match the observed level of transmitted flux. We also show that our blazar-heated model matches the data better than standard simulations even when such a rescaling is allowed. This concordance between Lyman-alpha data and simulations, which are based on the most recent cosmological parameters, suggests that the inclusion of blazar heating alleviates previous tensions on constraints for sigma_8 derived from Lyman-alpha measurements and other cosmological data. [abridged]
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