First cosmological constraints combining Planck with the recent gravitational-wave standard siren measurement of the Hubble constant

Eleonora Di Valentino, Alessandro Melchiorri

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    Abstract

    The recent observations of gravitational-wave and electromagnetic emission produced by the merger of the binary neutron-star system GW170817 have opened the possibility of using standard sirens to constrain the value of the Hubble constant. While the reported bound of H0=70-8+12 at 68% C.L. is significantly weaker than those recently derived by observations of Cepheid variables, it does not require any form of cosmic distance ladder and can be considered as complementary and, in principle, more conservative. Here we combine, for the first time, the new measurement with the Planck cosmic microwave background (CMB) observations in a 12 parameter extended ΛCDM scenario, where the Hubble constant is weakly constrained from CMB data alone and bound to a low value H0=55-20+7 km/s/Mpc at 68% C.L. We point out that the non-Gaussian shape of the GW170817 bound makes lower values of the Hubble constant in worse agreement with observations than what is expected from a Gaussian form. The inclusion of the new GW170817 Hubble constant measurement therefore significantly reduces the allowed parameter space, improving the cosmological bounds on several parameters as the neutrino mass, curvature, and dark energy equation of state.

    Original languageEnglish
    Article number041301
    JournalPhysical Review D
    Volume97
    Issue number4
    Early online date23 Feb 2018
    DOIs
    Publication statusPublished - 2018

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