星系中合并中子星的预测速率
Predicted rates of merging neutron stars in galaxies
摘要：
在这项工作中，我们计算合并中子星（MNS）在不同的形态类型的星系的比率，以及在宇宙的一个单一的体积，采用不同的宇宙学方案的宇宙MNS率。我们的目标是提供预测的kilonova率为未来的观测在低和高红移。在所采用的星系模型中，我们考虑到生产的r-过程元素的MNS或核心坍缩超新星。在计算MNS率，我们采用一个恒定的总时间延迟合并（10百万年）或分布函数的延迟。我们的主要结论是：i）我们银河系中观测到的当前时间MNS速率可以很好地用常数时间延迟或分布函数$\propto t^{-1}$再现。只要延迟时间较短且恒定，仅用MNS就能很好地再现银河系中的[Eu/Fe]与[Fe/H]关系。如果采用延迟分布函数，则也需要有核心坍缩的超新星。（2）无论是纯光度演化还是典型的等级宇宙学，现代宇宙MNS速率都可以很好地再现，而螺旋是其主要贡献者。（3）在等级宇宙学中，螺旋是宇宙MNS的主要贡献者。在纯光度演化的情况下，螺旋是本地的主要贡献者，而在高红移椭圆占主导地位。（iv）在观测导出的宇宙学分级方案中，如果采用延迟分布函数，则所预言的宇宙MNS速率与短伽马射线暴的宇宙速率符合得很好。v）未来在椭圆星系中对Kilonovae的观测将允许在常数或时间延迟分布之间以及在不同的宇宙学场景之间解开纠缠。
英文摘要：
In this work, we compute rates of merging neutron stars (MNS) in galaxies of different morphological type, as well as the cosmic MNS rate in a unitary volume of the Universe adopting different cosmological scenarios. Our aim is to provide predictions of kilonova rates for future observations both at low and high redshift. In the adopted galaxy models, we take into account the production of r-process elements either by MNS or core-collapse supernovae. In computing the MNS rates we adopt either a constant total time delay for merging (10 Myr) or a distribution function of such delays. Our main conclusions are: i) the observed present time MNS rate in our Galaxy is well reproduced either with a constant time delay or a distribution function $\propto t^{-1}$. The [Eu/Fe] vs. [Fe/H] relation in the Milky Way can be well reproduced with only MNS, if the time delay is short and constant. If the distribution function of delays is adopted, core-collapse supernovae as are also required. ii) The present time cosmic MNS rate can be well reproduced in any cosmological scenario, either pure luminosity evolution or a typical hierarchical one, and spirals are the main contributors to it. iii) The spirals are the major contributors to the cosmic MNS at all redshifts in hierarchical scenarios. In the pure luminosity evolution scenario, the spirals are the major contributors locally, whereas at high redshift ellipticals dominate. iv) The predicted cosmic MNS rate well agrees with the cosmic rate of short Gamma Ray Bursts if the distribution function of delays is adopted, in a cosmological hierarchical scenario observationally derived. v) Future observations of Kilonovae in ellipticals will allow to disentangle among constant or a distribution of time delays as well as among different cosmological scenarios.
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