LIGO Document P2100185-v5

Constraints on the cosmic expansion history from GWTC-3

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19 Nov 2021, 04:12
We use 47 gravitational-wave sources from the Third LIGO-Virgo-KAGRA Gravitational-Wave Transient Catalog (GWTC-3) to estimate the Hubble parameter \( H(z) \), including its current value, the Hubble constant \( H_0 \). Each gravitational-wave (GW) signal provides the luminosity distance to the source and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and \( H(z) \). The source mass distribution displays a peak around \( 34\, {\rm M_\odot} \), followed by a drop-off. Assuming this mass scale does not evolve with redshift results in a \( H(z) \) measurement, yielding \( H_0=68^{+13}_{-7} {\rm km\,s^{-1}\,Mpc^{-1}} \) (\( 68\% \) credible interval) when combined with the \( H_0 \) measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 13% with respect to the \( H_0 \) estimate from GWTC-1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event's potential hosts. Assuming a fixed BBH population, we estimate a value of \( H_0=68^{+8}_{-6} {\rm km\,s^{-1}\,Mpc^{-1}} \) with the galaxy catalog method, an improvement of 41% with respect to our GWTC-1 result and 20% with respect to recent \( H_0 \) studies using GWTC-2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about \( H_0 \)) is the well-localized event GW190814.
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The software used to produce the results in this paper can be downloaded from


Data results in the form of posterior samples for the cosmological and population parameters (icarogw) and Hubble constant posteriors (GWcosmo) are provided on Zenodo DOI: 10.5281/zenodo.5645777.

Zenodo contains also the GLADE+ galaxy catalog used to produce the GWcosmo results and example scripts to run the code.

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