Image Details
GWTC-4.0: Population Properties of Merging Compact Binaries
A. G. Abac et al 2026 The Astrophysical Journal Letters 1005 .
Caption: Figure 2.
A comparison of the merger rate at redshift z = 0, as a function of component mass for the FULLPOP-4.0 and BGP models. In the upper panel, we show the merger rate as a function of primary mass, marginalized over secondary mass. In the lower panel, we show the merger rate as a function of the secondary mass, marginalized over the primary mass. At m2 = 5 M⊙, the FULLPOP-4.0 model transitions to an alternative pairing function to allow for NSBHs, hence the discontinuity in the secondary mass. The median of the inferred merger rate is shown with a solid line, and the 90% credible interval is shown in the shaded region. The BGP weakly modeled approach has larger uncertainties due to increased flexibility. Both the strongly modeled and weakly modeled approaches find local maxima in the merger rate at m2 ∼ 1–2 M⊙ and m2 ∼ 6.5–9 M⊙ in the secondary-mass distribution. However, the BGP model does not confidently recover the low mass peaks in the primary-mass distribution. In the inset, we show the FULLPOP-4.0 inferred gap depth parameter A (see Appendix B.1), where A = 1 (a completely empty gap) is disfavored.
© 2026. The Author(s). Published by the American Astronomical Society.