标题： 超新星遗迹中微子背景的谱及其星系演化 显示英文标题

标题： Spectrum of the Supernova Relic Neutrino Background and Evolution of Galaxies

摘要： 我们用基于星系演化的合成方法的标准模型推导出的一个现实的、随时间变化的超新星爆发率，计算了由宇宙中曾经发生的引力坍缩驱动的超新星遗迹中微子背景（SRN）的能谱。这里展示的SRN能谱是目前最现实的，因为以前理论预测中的最大不确定性来自于对超新星爆发率不切实际的假设。SRN是超级神冈探测器（SK）的目标之一，如果能够检测到的话，它将提供一种新的工具来探测宇宙中超新星爆发的历史。因此，本文计算了SK上的预期事件率。我们的主要结果包括：(1) 在星系演化的早期阶段，超新星爆发率要高得多，在低能区$\ltilde 5$MeV的SRN能谱中出现了一个峰值；(2) SRN通量与哈勃常数（$H_0$）大致呈正比关系$H_0^2$，并且仅对宇宙物质密度参数（$\Omega_0$）和宇宙学常数（$\lambda_0$）有较弱依赖；(3) 在可观测的能量范围内，SK上可能的事件率为1.2 yr$^{-1}$。如此低的事件率主要是由于当前平均的超新星爆发率非常低，这是对星系形态类型的平均值。在我们的模型中，最乐观的估计是4.7 yr$^{-1}$，如果检测到更多的事件，我们将不得不重新考虑我们对引力坍缩驱动的超新星和星系演化现状的理解。 显示英文摘要

摘要： The spectrum of the supernova relic neutrino background (SRN) from collapse-driven supernovae ever occurred in the universe is calculated by using a realistic, time-dependent supernova rate derived from a standard model of galaxy evolution based on the population synthesis method. The SRN spectrum we show here is the most realistic at present, because the largest uncertainty in previous theoretical predictions has come from unrealistic assumptions of the supernova rate so far made. The SRN is one of the targets of the Superkamiokande (SK) detector which will be constructed in a year and the SRN, if at all detected, would provide a new tool to probe the history of supernova explosions in the universe. The expected event rate at the SK is therefore calculated in this paper. Our major results include: (1) the supernova rate is much higher in the early phase of evolution of galaxies and there appears a hump in the SRN spectrum in the low-energy region of $\ltilde 5$ MeV, (2) the SRN flux depends on the Hubble constant ($H_0$) in a way approximately proportional to $H_0^2$ and only weakly on the density parameter of the universe ($\Omega_0$) and a cosmological constant ($\lambda_0$), and (3) the plausible event rate at the SK is 1.2 yr$^{-1}$ in the observable energy range. Such a low event rate is due mainly to a quite low supernova rate at present which is averaged over the morphological types of galaxies. The most optimistic rate in our model is found to be 4.7 yr$^{-1}$, and if more events are detected, we will have to reconsider our current understanding of collapse-driven supernovae and evolution of galaxies.