Cosmological inference using only gravitational wave observations of binary neutron stars

Messenger, C. (2017) Cosmological inference using only gravitational wave observations of binary neutron stars. Physical Review D, 95(4), 043502. (doi: 10.1103/PhysRevD.95.043502)

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Gravitational waves emitted during the coalescence of binary neutron star systems are self-calibrating signals. As such, they can provide a direct measurement of the luminosity distance to a source without the need for a cross-calibrated cosmic distance-scale ladder. In general, however, the corresponding redshift measurement needs to be obtained via electromagnetic observations since it is totally degenerate with the total mass of the system. Nevertheless, Fisher matrix studies have shown that, if information about the equation of state of the neutron stars is available, it is possible to extract redshift information from the gravitational wave signal alone. Therefore, measuring the cosmological parameters in pure gravitational-wave fashion is possible. Furthermore, the huge number of sources potentially observable by the Einstein Telescope has led to speculations that the gravitational wave measurement is potentially competitive with traditional methods. The Einstein Telescope is a conceptual study for a third generation gravitational wave detector which is designed to yield 103–107 detections of binary neutron star systems per year. This study presents the first Bayesian investigation of the accuracy with which the cosmological parameters can be measured using information coming only from the gravitational wave observations of binary neutron star systems by the Einstein Telescope. We find, by direct simulation of 103 detections of binary neutron stars, that, within our simplifying assumptions, H0, Ωm, ΩΛ, w0 and w1 can be measured at the 95% level with an accuracy of ∼8%, 65%, 39%, 80% and 90%, respectively. We also find, by extrapolation, that a measurement accuracy comparable with current measurements by Planck is possible if the number of gravitational wave events observed is Oð106–7Þ. We conclude that, while not competitive with electromagnetic missions in terms of significant digits, gravitational waves alone are capable of providing a complementary determination of the dynamics of the Universe.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Messenger, Dr Christopher
Authors: Messenger, C.
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Centre:College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN (Online):2470-0029
Published Online:02 February 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Physical Review D 94(4):043502
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
624341Investigations in Gravitational Radiation / Particle Astrophysics Capital equipmentSheila RowanScience & Technologies Facilities Council (STFC)ST/L000946/1S&E P&A - PHYSICS & ASTRONOMY