类星体再电离HeII过程中的光加热和硬光子的命运
Photo-heating and the fate of hard photons during the reionisation of HeII by quasars
摘要：
我们使用的分析和数值参数相结合，考虑类星体的光加热在HeII再电离的星系际介质（IGM）的热演化的影响。我们证明，快速（Δz< 0.1-0.2），强（ΔT > 10^4 K）的光加热很难在整个IGM中实现，除非类星体的光谱比目前的观测限制所暗示的要硬得多。虽然通过IGM中的密集区域过滤固有类星体辐射确实增加了每次HeII光电离的平均过剩能量，但它也削弱了辐射强度并降低了光电离速率，防止了在短于局部光电离时间尺度的时间间隔内快速加热。此外，负责最强加热的硬光子更有可能将其能量沉积在密集的团块中。然而，这种团块的丰度是不确定的和依赖于模型的，导致光加热速率的相当大的不确定性。尽管如此，尽管一些IGM可能会长时间暴露在硬化和弱化的电离背景下，但大多数IGM必须被更丰富、更软的光子重新电离，并相应地以适度的加热速率（ΔT < 10^4 K）。化石类星体HeIII区域的重复电离不会增加净加热，因为这些区域的复合时间通常超过IGM冷却时间和连续几轮类星体活动之间的平均时滞。详细的视线辐射转移模拟证实了这些预期，并预测丰富的热结构在IGM在HeII再电离。[摘要]
英文摘要：
We use a combination of analytic and numerical arguments to consider the impact of quasar photo-heating during HeII reionisation on the thermal evolution of the intergalactic medium (IGM). We demonstrate that rapid (Δz< 0.1-0.2), strong (ΔT > 10^4 K) photo-heating is difficult to achieve across the entire IGM unless quasar spectra are significantly harder than implied by current observational constraints. Although filtering of intrinsic quasar radiation through dense regions in the IGM does increase the mean excess energy per HeII photo-ionisation, it also weakens the radiation intensity and lowers the photo-ionisation rate, preventing rapid heating over time intervals shorter than the local photo-ionisation timescale. Moreover, the hard photons responsible for the strongest heating are more likely to deposit their energy inside dense clumps. The abundance of such clumps is, however, uncertain and model-dependent, leading to a fairly large uncertainty in the photo-heating rates. Nevertheless, although some of the IGM may be exposed to a hardened and weakened ionising background for long periods, most of the IGM must instead be reionised by the more abundant, softer photons and with accordingly modest heating rates (ΔT < 10^4 K). The repeated ionisation of fossil quasar HeIII regions does not increase the net heating because the recombination times in these regions typically exceed the IGM cooling times and the average time lag between successive rounds of quasar activity. Detailed line-of-sight radiative transfer simulations confirm these expectations and predict a rich thermal structure in the IGM during HeII reionisation. [Abridged]
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