局域宇宙中致密双星的总合并率
The Total Merger Rate of Compact Object Binaries In The Local Universe
摘要：
利用粒子数合成方法，计算了双中子星、双黑洞和黑洞-中子星双星在局域宇宙中的总合并率。这些紧凑的双星是LIGO和VIRGO探测引力波的主要候选源。我们占合并起源于外地人口和密集的星团。对于这两个种群，我们使用相同的恒星演化处理方法。我们的结果表明，合并率的双中子星和黑洞-中子星双星的强烈主导的领域人口，而合并黑洞双星的形成更有效地在密集的星团。双致密天体的总合并率敏感地依赖于稠密星系团的初始质量分数f_cl（很大程度上未知）。当f_cl < 0.0001时，Advanced LIGO的探测率将主要由双中子星合并的场粒子数决定，探测次数虽然少，但意义重大，约为20年^-1。然而，当星系团中的质量分数较高时（f_cl > 0.001），探测率将主要由来自致密星系团的大量双黑洞合并所决定，而且探测率会高得多，约为25 ~ 300年^-1。此外，我们表明，一旦合并的双黑洞被检测到，它是很容易区分系统中形成的领域和密集的集群，因为啁啾的质量分布是惊人的不同。最后，我们指出在星系际空间中可能存在并合黑洞双星。
英文摘要：
Using a population synthesis approach, we compute the total merger rate in the local Universe for double neutron stars, double black holes, and black hole -- neutron star binaries. These compact binaries are the prime source candidates for gravitational-wave detection by LIGO and VIRGO. We account for mergers originating from field populations and from dense stellar clusters. For both populations we use the same treatment of stellar evolution. Our results indicate that the merger rates of double neutron stars and black hole -- neutron star binaries are strongly dominated by field populations, while merging black hole binaries are formed much more effectively in dense stellar clusters. The overall merger rate of double compact objects depends sensitively on the (largely unknown) initial mass fraction contained in dense clusters f_cl. For f_cl < 0.0001, the Advanced LIGO detection rate will be dominated by field populations of double neutron star mergers, with a small but significant number of detections ~20 yr^-1. However for a higher mass fraction in clusters, f_cl > 0.001, the detection rate will be dominated by numerous mergers of double black holes originating from dense clusters, and it will be considerably higher, ~25 - 300 yr^-1. In addition, we show that, once mergers of double black holes are detected, it is easy to differentiate between systems formed in the field and in dense clusters, since the chirp mass distributions are strikingly different. Finally, we point out that there may exist a population of merging black hole binaries in intergalactic space.
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