Abstract
We report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star–black hole mergers. We infer the binary neutron star merger rate to be between 10 and and the neutron star–black hole merger rate to be between 7.8 and , assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and at a fiducial redshift (). The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to with for . Using both binary neutron star and neutron star–black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from to . We confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. We also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of and . While we continue to find that the mass distribution of a binary’s more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately , which would indicate the presence of a upper mass gap. Observed black hole spins are small, with half of spin magnitudes below . While the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also observe evidence of misalignment of spins relative to the orbital angular momentum.
22 More- Received 4 February 2022
- Revised 28 October 2022
- Accepted 19 December 2022
DOI:https://doi.org/10.1103/PhysRevX.13.011048
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Gravitational waves from mergers of binary black holes and neutron stars can reveal the properties of unique single sources. However, a population is needed to shed light on how these systems form and evolve throughout the Universe. Researchers are particularly interested in measuring the distributions of the mass and spin of compact objects, since these properties can provide details about how such objects form. Using data from the first three observing runs of the LIGO and Virgo gravitational-wave detectors, we report on the population properties of 76 compact binary mergers.
We infer a binary neutron star merger rate of about and a neutron star–black hole rate of about . The merger rate for binary black holes in the relatively local Universe is about , but was higher in the past, reflecting observed trends in star formation.
We find a flat neutron star mass distribution from 1.2 to 2.0 solar masses. The merger rate sharply declines above the expected maximum neutron star mass, but we cannot confirm or rule out the existence of a mass gap between neutron stars and black holes. The black hole mass distribution has peaks at about 10 and 35 solar masses for the more massive of the two black holes in a binary. We observe no evidence of a suppressed merger rate above 60 solar masses, which would indicate the presence of an upper mass gap. While most spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population.
The growing catalog of compact binary mergers is letting us begin to delve into the formation and evolutionary pathways of these objects. With more data from future observing runs, we expect to eventually place new constraints on phenomena such as how stars die, how compact objects couple up dynamically, and what the Universe is made of.