The Proximity Effect in Quasar Spectra as an Astrophysical Tool

我们建议对高红移类星体光谱中的“接近效应”进行全面的研究。这一现象描述了由于单个类星体的作用，星系间氢（也包括氦）的吸收减少。这些提供了额外的电离光子，而不是来自宇宙紫外线背景的光子，导致类星体周围mpc尺度上的中性气柱密度降低。我们已经起草了一套观测实验来利用邻近效应作为天体物理工具。我们研究的指导性科学问题是宇宙紫外线背景（UVB）是如何形成和受到离散源的影响的。观测结果将由宇宙学结构形成的气体动力学模拟结果补充和校准。我们将能够以前所未有的统计精度估计中波紫外线的强度及其红移的演变。我们将研究单个类星体与中波紫外线光谱波动之间的联系。这些测量将提供对z ~ 2-4附近“类星体时代”宇宙辐射传输特性的深入了解。与此同时，我们将能够限制类星体的一些基本但鲜为人知的数量：它们的生命时间，以及类星体辐射输出的各向异性程度。

We propose a comprehensive investigation of the 'proximity effect' in the spectra of high-redshift quasars. This phenomenon describes the reduced absorption by intergalactic hydrogen (and also helium) by the action of individual quasars. These provide additional ionizing photons in excess to those from the cosmic UV background, leading to a reduction of neutral gas column densities on Mpc-scales around the quasars. We have drafted a set of observational experiments to exploit the proximity effect as an astrophysical tool. The guiding scientific question of our investigation is how the cosmic UV background (UVB) is formed and influenced by discrete sources. The observations will be complemented by and calibrated with results from gasdynamical simulations of cosmological structure formation. We will be able to estimate the intensity of the UVB and its evolution with redshift with unprecedented statistical accuracy. We will study the connection between individual quasars and spectral fluctuations of the UVB. These measurements will provide insights into the radiative transfer properties of the universe in the 'quasar epoch' around z ~ 2-4. At the same time we will be able to constrain some fundamental, but poorly known quantities of quasars: Their life times, and the degree of anisotropy in the quasar radiative output.