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

Sourav Chatterjee, Carl L. Rodriguez, Vicky Kalogera, Frederic A. Rasio

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


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 1σ of the mass distribution obtained from our models for clusters with Z/Z ≳ 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 ≲ 0.25. On the other hand, GW150914 is more massive (beyond 1σ) than typical BBHs from even the lowest-metallicity (Z/Z = 0.005) clusters we consider, but is within 2σ of the intrinsic mass distribution from our cluster models with Z/Z ≲ 0.05; of course, detection biases also push the observed distributions toward higher masses.

Original languageEnglish (US)
Article numberL26
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Feb 20 2017


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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