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.