bpass predictions for binary black hole mergers

Abstract

Using the Binary Population and Spectral Synthesis code BPASS, we have calculated the rates, timescales and mass distributions for binary black hole mergers as a function of metallicity. We consider these in the context of the recently reported 1st LIGO event detection. We find that the event has a very low probability of arising from a stellar population with initial metallicity mass fraction above Z = 0.010 (Z > ∼ 0.5 Z ⊙ ). Binary black hole merger events with the reported masses are most likely in populations below 0.008 (Z < ∼ 0.4 Z ⊙ ). Events of this kind can occur at all stellar population ages from 3 Myr up to the age of the universe, but constitute only 0.1 to 0.4 per cent of binary BH mergers between metallicities of Z = 0.001 to 0.008. However at metallicity Z = 10 −4 , 26 per cent of binary BH mergers would be expected to have the reported masses. At this metallicity the progenitor merger times can be close to ≈ 10Gyr and rotationallymixed stars evolving through quasi-homogeneous evolution, due to mass transfer in a binary, dominate the rate. The masses inferred for the black holes in the binary progenitor of GW 150914 are amongst the most massive expected at anything but the lowest metallicities in our models. We discuss the implications of our analysis for the electromagnetic follow-up of future LIGO event detections.

Binary Black Hole Mergers in the First Advanced LIGO Observing Run

“…[168][169][170][171][172][173]), possibly from population III binaries [174,175], or chemically homogeneous evolution in close tidally locked binaries [176,177]. All of these channels have been shown to be consistent with the GW150914 discovery [178][179][180][181][182][183][184][185][186].…”

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

“…Isolated binary evolution in galactic fields classically proceeds via a common envelope [97][98][99][100][101][102][103][104][105]. Variants avoiding common-envelope evolution include (quasi-)chemically homogeneous evolution of massive tidally locked binaries [101,106,107], or through stable mass transfer in Population I [108,109] or Population III binaries [110,111].…”

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

“…The possibility that the high mass cutoff could be smaller than the value of 100 M , as explored by Tsujimoto et al (1995), seems to be excluded by the statistics of gravitational wave sources, and in particular by the event GW150914 due to the merger of two ∼30 M black holes (Abbott et al 2016). High-mass black holes shoud not be very rare, which implies that the IMF extends up to at least 100 M and probably up to 150 M (Belczynski et al 2016), and even up to 300 M (Eldridge & Stanway 2016). On the other hand, we tested the hypothesis of a top-heavy IMF (Tsujimoto & Bekki 2012), by adopting their choice x IMF = 1.05 for the model shown in to be at [Fe/H] ∼ −0.3 from data provided by Johnson et al (2014) and at −0.6 < [Fe/H] < −0.5 from that provided by Bensby et al (2013) and Ryde et al (2010).…”