Impact of Bayesian Priors on the Characterization of Binary Black Hole Coalescences
In a regime where data are only mildly informative, prior choices can play a significant role in Bayesian statistical inference, potentially affecting the inferred physics. We show this is indeed the case for some of the parameters inferred from current gravitational-wave measurements of binary black hole coalescences. We reanalyze the first detections performed by the twin LIGO interferometers using alternative (and astrophysically motivated) prior assumptions. We find different prior distributions can introduce deviations in the resulting posteriors that impact the physical interpretation of these systems. For instance, (i) limits on the 90% credible interval on the effective black hole spin χ_(eff) are subject to variations of ∼10% if a prior with black hole spins mostly aligned to the binary's angular momentum is considered instead of the standard choice of isotropic spin directions, and (ii) under priors motivated by the initial stellar mass function, we infer tighter constraints on the black hole masses, and in particular, we find no support for any of the inferred masses within the putative mass gap M ≲ 5 M⊙.
© 2017 American Physical Society. Received 24 August 2017; published 20 December 2017. We thank Thomas Dent, Jim Fuller, Chris Pankow, Harald Pfeiffer, Vivien Raymond, and Leo Stein for various stimulating discussions. We thank Christopher Berry, James Clark, Will Farr, Heather Fong, Prayush Kumar, Richard O'Shaughnessy, Harald Pfeiffer, and John Veitch for discussions on the use of the volumetric prior and making their implementation public. We thank Lisa Barsotti for providing a simulated noise spectral density for the analysis of the GW170104 software replica. S. V. acknowledges support of MIT through the Solomon Buchsbaum Research Fund, the National Science Foundation, and the LIGO Laboratory. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation and operates under cooperative agreement PHY-0757058. D. G. is supported by NASA through Einstein Postdoctoral Fellowship Grant No. PF6-170152 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under Contract NAS8-03060. The authors acknowledge the LIGO Data Grid clusters. This project started during the workshop "Strong Gravity and Binary Dynamics with Gravitational Wave Observations," funded through NSF CAREER Grant No. PHY-1055103. This paper carries LIGO Document No. P1700176.
Submitted - 1707.04637.pdf
Published - PhysRevLett.119.251103.pdf