超星系光电离背景中的含时涨落
Time-dependent fluctuations in the metagalactic photoionization background
摘要：
我们提出了一种计算宇宙学光电离辐射背景中随时间变化的涨落的形式主义，将背景涨落模型扩展到稳态近似之外。假设光电离背景主要是类星体和星系，我们应用这种形式估计了HI LyA通量红移空间功率谱及其在红移2<z<4处的空间关联函数的涨落.我们表明，由于离散源的功率谱中的散粒噪声被强烈抑制相对于稳态值在低波数的源的寿命成比例的一个因素，这种抑制可用于约束类星体的寿命。总HI LyA功率谱，包括散粒噪声的影响在百分之几十的短尺度上，和多达一个数量级或更多的尺度上超过平均freepath.The空间关联函数同样被发现是敏感的散粒噪声，虽然适度不敏感的非散粒噪声贡献的时间依赖性的影响。光电离率的波动大大改变了关联函数中重子声振荡峰的形状，包括其位置的小幅增加，必须考虑到这一点，以避免基于峰位置对宇宙学参数的偏置估计。我们简要地调查解决全频率相关的方程，发现它同意与频率无关，以优于百分之精度。简单的公式提供的功率谱的波动的光电离率，近似的全部计算。
英文摘要：
We present a formalism for computing time-dependent fluctuations in the cosmological photoionizing radiation background, extending background fluctuations models beyond the steady-state approximation. We apply this formalism to estimate fluctuations in the HI LyA flux redshift space power spectrum and its spatial correlation function at redshifts 2<z<4, assuming the photoionization background is dominated by Quasi-stellar Objects (QSOs) and/or galaxies. We show the shot noise in the power spectrum due to discrete sources is strongly suppressed relative to the steady-state value at low wavenumbers by a factor proportional to the lifetime of the sources, and that this suppression may be used to constrain QSO lifetimes. The total HI LyA power spectrum including shot noise is affected at tens of percent on short scales, and by as much as an order of magnitude or more on scales exceeding the mean free path. The spatial correlation function is similarly found to be sensitive to the shot noise, although moderately insensitive to the effects of time-dependence on the non-shotnoise contribution. Photoionization rate fluctuations substantially modify the shape of the Baryonic Acoustic Oscillation peak in the correlation function, including a small increase in its position that must be accounted for to avoid biasing estimates of cosmological parameters based on the peak position. We briefly investigate solving the full frequency dependent equation, finding that it agrees with the frequency-independent to better than percent accuracy. Simple formulas are provided for the power spectrum of fluctuations in the photoionization rate that approximate the full computations.
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