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GWTC-4.0: Population Properties of Merging Compact Binaries
A. G. Abac et al 2026 The Astrophysical Journal Letters 1005 .
Caption: Figure 14.
The inferred mean (top) and width (bottom) of the χeff distribution as a function of redshift for the LINEAR model (blue) and the SPLINE model (orange). The shaded regions give the 90% credible intervals. The gray dashed line indicates the redshift under which 90% of the cumulative posterior probability lies across all events in GWTC-4.0. Therefore, inferences above this redshift are dominated by the prior or population model. Note the logarithmic scale on the width (bottom panel). In either model, we find evidence that the width of the effective inspiral spin distribution increases with redshift up to z ∼ 1.
© 2026. The Author(s). Published by the American Astronomical Society.