Velocity correction for Hubble constant measurements from standard sirens

¹ Institut d’Astrophysique de Paris (IAP), CNRS & Sorbonne Université, UMR 7095, 98bis bd Arago, 75014 Paris, France
e-mail: s.mukherjee@uva.nl, mukherje@iap.fr
² Institut Lagrange de Paris (ILP), Sorbonne Universités, 98bis Boulevard Arago, 75014 Paris, France
³ Gravitation Astroparticle Physics Amsterdam (GRAPPA), Anton Pannekoek Institute for Astronomy and Institute for High-Energy Physics, University of Amsterdam, Science Park 904, 1090 GL Amsterdam, The Netherlands
⁴ The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova University Centre, 106 91 Stockholm, Sweden
⁵ Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA
⁶ Imperial Centre for Inference and Cosmology (ICIC) & Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
⁷ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540, USA
⁸ Research Center for the Early Universe, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

Received: 18 September 2019
Accepted: 24 November 2020

Abstract

Gravitational wave (GW) sources are an excellent probe of the luminosity distance and offer a novel measure of the Hubble constant, H₀. This estimation of H₀ from standard sirens requires an accurate estimation of the cosmological redshift of the host galaxy of the GW source after correcting for its peculiar velocity. The absence of an accurate peculiar velocity correction affects both the precision and accuracy of the measurement of H₀, particularly for nearby sources. Here, we propose a framework to incorporate such a peculiar velocity correction for GW sources. A first implementation of our method to the event GW170817, combined with observations taken with Very Large Baseline Interferometry (VLBI), leads to a revised value of H₀ = 68.3_−4.5^+4.6 km s⁻¹ Mpc⁻¹. While this revision is minor, it demonstrates that our method makes it possible to obtain unbiased and accurate measurements of H₀ at the precision required for the standard siren cosmology.