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The binary black hole merger rate of the Universe: comparison of our
predictions with the LIGO observational results.

Download a PDF of the plot (right click and save)

The right panel shows the range of BH-BH coalescence rates (9-240 Gpc^{-3} yr^{-1})
consistent with LIGO. For comparison, we also
show the predictions using our four evolutionary models M1 (standard physics),
M2 (easy common envelope), M3 (high black hole natal kicks), and M4 (moderate
black hole natal kicks). Note that models M2 and M3 are already excluded by
LIGO observations. Our standard model M1 (220 Gpc^{-3} yr^{-1}) and model with
moderate BH kicks M4 (11.3 Gpc^{-3} yr^{-1}) are within the LIGO estimate. For more
details on the models see
"The first gravitational-wave
source from the isolated evolution of two 40-100 Msun stars", Nature, June 23, 2016.

In the left panel we show merger rate density as a function of the total
mass of the binary. The blue markers represent the LIGO detections of binary
black holes in O1. Because of degeneracies
that impair LIGO's ability to tightly constrain the source distance and
hence redshift, we report (on the horizontal axis) an observationally
well-constrained quantity: the apparent (redshifted) mass. For comparison,
the solid red line shows how binary black holes in different redshifted mass
intervals contribute to the overall merger rate for M1. Finally, for a
sense of scale, the solid blue line characterizes the mass-dependent
sensitivity of LIGO to binaries of different redshifted mass during the O1
observations. The detections are expected in the total mass range of
20--80 Msun, where our model (red line) approaches LIGO sensitivity (blue
line).

This figure shows that the three BH-BH merger events detected by LIGO are
consistent with our predictions for the O1 rate as well as our prediction
for the O1 detected mass distribution.

Projection of our models into the future implies BH-BH detection rate of
90-1700 yr^{-1} (models M4-M1) for the design sensitivity of advanced LIGO
(2019-2020). Taking into account the current LIGO duty cycle of 30 percent
(two detectors operating at the same time) this translates to detection of
about 30-500 BH-BH mergers per year.

This website will be kept updated with new models and observations as they
appear.