Interpreting the transmission windows of distant quasars
Interpreting the transmission windows of distant quasars
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DOI：
10.1111/j.1365-2966.2009.14699.x
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发表时间：
2009-02
影响因子：
4.8
通讯作者：
A. Maselli;A. Ferrara;S. P. M. F. Astrophysics;Garching;H Germany;Scuola Normale Superiore Pisa;Italy.;Osservatorio Astronomico di Roma;M. Porzio
中科院分区：
文献类型：
--
作者：
A. Maselli;A. Ferrara;S. P. M. F. Astrophysics;Garching;H Germany;Scuola Normale Superiore Pisa;Italy.;Osservatorio Astronomico di Roma;M. Porzio
我们提出了视收缩准则（ASC）来解释高z类星体吸收光谱中透射通量窗口的空间范围rw。ASC可以区分R w对应类星体HII区域的物理尺寸R HII或距离R max w的两种情况，在这两种情况下，透射通量降至=0.1，并出现Gunn-Peterson （GP）波谷。在第一种情况下[H区（HR）制度]，可以确定星系间介质的平均HI分数，x HI；在第二个[接近区（PR）制度]中，R W的值允许人们测量局部光离率和光离率的局部增强，Γ G，由于附近/介入星系。ASC在辐射传输+光滑粒子流体力学数值模拟中进行了测试，并应用于15个高z （z > 5.8）类星体光谱样品。所有类星体样本都处于PR区；因此，观测到的光谱性质（内部通量分布、透射窗口范围）不能可靠地约束x HI的值。四个样本类星体显示了可能由星系过度密度产生的局部光离率增强（高达50%）的证据。我们讨论了这一结果的可能解释和不确定性。
We propose the apparent shrinking criterion (ASC) to interpret the spatial extent, R W , of transmitted flux windows in the absorption spectra of high-z quasars. The ASC can discriminate between the two regimes in which R w corresponds either to the physical size, R HII , of the quasar H II region or to the distance, R max W , at which the transmitted flux drops to =0.1 and a Gunn-Peterson (GP) trough appears. In the first case [H II region (HR) regime], one can determine the intergalactic medium mean H I fraction, x HI ; it the second [proximity region (PR) regime], the value of R W allows one to measure the local photoionization rate and the local enhancement of the photoionization rate, Γ G , due to nearby/intervening galaxies. The ASC has been tested against radiative transfer+smoothed particle hydrodynamics numerical simulations, and applied to a sample of 15 high-z (z > 5.8) quasar spectra. All sample quasars are found to be in the PR regime; hence, their observed spectral properties (inner flux profile, extent of transmission window) cannot reliably constrain the value of x HI . Four sample quasars show evidence for a local enhancement (up to 50 per cent) in the local photoionization rate possibly produced by a galaxy overdensity. We discuss the possible interpretations and uncertainties of this result.