Title: Background power subtraction in Lyman-alpha forest Show Chinese title

Title: 背景功率减去在莱曼-α森林中

Abstract: When measuring the one-dimensional power spectrum of the Ly$\alpha$ forest, it is common to measure the power spectrum in flux fluctuations red-ward of the Ly$\alpha$ emission of quasars and subtract this power from the measurements of the Ly$\alpha$ flux power spectrum. This removes excess power present in the Ly$\alpha$ forest which is believed to be dominated by metal absorption by the low-redshift metals uncorrelated with the neutral hydrogen aborbing in Ly$\alpha$. In this brief report we note that, assuming the contaminants are additive in optical depth, the correction contains a second order term. We estimate the magnitude of this term for two currently published measurements of the 1D Ly$\alpha$ flux power spectrum and show that it is negligible for the current generation of measurements. However, future measurements will have to take this into account when errorbars improve by a factor of two or more. Show Chinese abstract

Abstract: 在测量类星体Ly$\alpha$森林的一维功率谱时，通常会在Ly$\alpha$发射线红移方向测量流量波动的功率谱，并从Ly$\alpha$流量功率谱的测量结果中减去这一功率。 这消除了Ly$\alpha$森林中存在的额外功率，据信这些功率主要由低红移金属吸收引起，与Ly$\alpha$中中性氢的吸收无关。 在本简短报告中我们注意到，假设污染物在光学深度上是相加的，修正中包含一个二阶项。 我们估计了这一项对于两个目前发表的1D Ly$\alpha$流量功率谱测量的大小，并表明对于当前一代的测量来说它是可以忽略的。 然而，未来测量在误差条改善两倍或更多时必须考虑这一点。