GW150914: Implications for the stochastic gravitational-wave background from binary black holes

Abstract

The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses≳30M⊙, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and AdvancedVirgo band for stochastic backgrounds (near 25 Hz), we predict ΩGWðf ¼ 25 HzÞ ¼ 1.1 þ2.7 −0.9 × 10−9 with 90% confidence. This prediction is robustly demonstrated for a variety of formation scenarios with different parameters. The differences betweenmodels are small compared to the statistical uncertainty arising from the currently poorly constrained local coalescence rate. We conclude that this background is potentially measurable by the Advanced LIGO and Advanced Virgo detectors operating at their projected final sensitivity.