An improved measurement of the flux distribution of the Lyα forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties
An improved measurement of the flux distribution of the Lyα forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties
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DOI：
10.1111/j.1365-2966.2007.12406.x
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发表时间：
2007-11
影响因子：
4.8
通讯作者：
T.-S. Kim;J. Bolton;M. Viel;M. Haehnelt;R. P. L. F. A. Potsdam;Potsdam;H Germany;I. O. Astronomy;Cambridge;UK.;M. F. Astrophysik;G. B. Muenchen;Inaf Trieste;Trieste;Italy.
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文献类型：
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作者：
T.-S. Kim;J. Bolton;M. Viel;M. Haehnelt;R. P. L. F. A. Potsdam;Potsdam;H Germany;I. O. Astronomy;Cambridge;UK.;M. F. Astrophysik;G. B. Muenchen;Inaf Trieste;Trieste;Italy.
我们已经进行了广泛的Voigt配置文件分析的中性氢（H i）和金属吸收存在于一个样本的18个高分辨率，高信噪比的类星体（QSO）光谱观察到的甚大望远镜紫外和视觉Echelle摄谱仪。我们使用这种分析来分离金属的贡献从H的吸收，并提出了一个改进的测量的通量概率分布函数（PDF）由于H i吸收单独在（z）= 2.07，2.52和2.94。通量PDF在归一化通量范围0.8 < F < 1.0内对连续拟合敏感，在0.2 < F < 0.8时对金属吸收敏感。与McDonald等人广泛使用的测量结果相比，我们对仅由H i吸收引起的通量PDF的新测量结果在0.2 < F < 0.8时系统性地降低了30%，基于凯克高分辨率中阶梯光谱仪数据的显著较小的样本。这种差异可能是由于我们改进了金属吸收和宇宙方差的去除，因为不同视线之间的通量PDF变化很大。在1.7 < z < 4处的H有效光学深度τ eff Ht最符合单次幂定律，τ eff HI =（0.0023 ± 0.0007）（1 + z）365±0.21，与先前根据可比数据测量的结果非常一致。如前所述，在高分辨率、高信噪比的数据中，噪声对通量分布的影响并不显著。
We have performed an extensive Voigt profile analysis of the neutral hydrogen (H i) and metal absorption present in a sample of 18 high-resolution, high signal-to-noise ratio quasi-stellar object (QSO) spectra observed with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph. We use this analysis to separate the metal contribution from the H absorption and present an improved measurement of the flux probability distribution function (PDF) due to H i absorption alone at (z) = 2.07,2.52 and 2.94. The flux PDF is sensitive to the continuum fit in the normalized flux range 0.8 < F < 1.0 and to metal absorption at 0.2 < F < 0.8. Our new measurements of the flux PDF due to H i absorption alone are systematically lower at 0.2 < F < 0.8 by up to 30 per cent compared to the widely used measurement of McDonald et al., based on a significantly smaller sample of Keck High Resolution Echelle Spectrometer data. This discrepancy is probably due to a combination of our improved removal of the metal absorption and cosmic variance, since variations in the flux PDF between different lines-of-sight are large. The H effective optical depth τ eff Ht at 1.7 < z < 4 is best fit with a single power law, τ eff HI = (0.0023 ± 0.0007)(1 + z) 365±0.21 , in good agreement with previous measurements from comparable data. As also found previously, the effect of noise on the flux distribution is not significant in high-resolution, high signal-to-noise ratio data.