Dynamical Formation of Low-mass Merging Black Hole Binaries like GW151226

作者：Chatterjee Sourav^*; Rodriguez Carl L; Kalogera Vicky; Rasio Frederic A

来源：Astrophysical Journal Letters, 2017, 836(2): L26.

DOI：10.3847/2041-8213/aa5caa

• black hole physics
• galaxies: star clusters: general
• globular clusters: general
• gravitational waves
• methods: numerical
• methods: statistical

Using numerical models for star clusters spanning a wide range in ages and metallicities (Z) we study the masses of binary black holes (BBHs) produced dynamically and merging in the local universe (z <= 0.2). After taking into account cosmological constraints on star formation rate and metallicity evolution, which realistically relate merger delay times obtained from models with merger redshifts, we show here for the first time that while old, metal-poor globular clusters can naturally produce merging BBHs with heavier components, as observed in GW150914, lower-mass BBHs like GW151226 are easily formed dynamically in younger, higher-metallicity clusters. More specifically, we show that the mass of GW151226 is well within 1 sigma of the mass distribution obtained from our models for clusters with Z/Z(circle dot) >= 0.5. Indeed, dynamical formation of a system like GW151226 likely requires a cluster that is younger and has a higher metallicity than typical Galactic globular clusters. The LVT151012 system, if real, could have been created in any cluster with Z/Z(circle dot) <= 0.25. On the other hand, GW150914 is more massive (beyond 1s) than typical BBHs from even the lowest-metallicity (Z/Z(circle dot) = 0.005) clusters we consider, but is within 2 sigma of the intrinsic mass distribution from our cluster models with Z/Z(circle dot) <= 0.05; of course, detection biases also push the observed distributions toward higher masses.

• 出版日期2017-2-20
• 单位MIT; 西北大学