An interacting dark sector and the first gravitational-wave standard siren detection

TL;DR

This paper combines gravitational-wave and electromagnetic data to constrain an interacting dark energy model, highlighting the importance of future gravitational-wave standard siren measurements for understanding dark energy and dark matter interactions.

Contribution

It provides the first joint analysis using gravitational-wave data to constrain an interacting dark energy model, emphasizing the role of GW measurements in cosmology.

Findings

GW170817 Hubble constant measurement aligns better with high-redshift data.

Local Hubble constant measurements influence dark sector coupling constraints.

Future GW standard siren data will be crucial for dark energy studies.

Abstract

After the first nearly simultaneous joint observations of gravitational-waves and electromagnetic emission produced by the coalescence of a binary neutron star system, another probe of the cosmic expansion which is independent from the cosmic distance ladder, became available. We perform a global analysis in order to constrain an interacting dark energy model, characterised by a conformal interaction between dark matter and dark energy, by combining current data from: $\textit{Planck}$ observations of the cosmic microwave background radiation anisotropies, and a compilation of Hubble parameter measurements estimated from the cosmic chronometers approach as well as from baryon acoustic oscillations measurements. Moreover, we consider two measurements of the expansion rate of the Universe today, one from the observations of the Cepheid variables, and another from the merger of the binary neutron star system GW170817. We find that in this interacting dark energy model, the influence of the local measurement of the Hubble constant mostly affects the inferred constraints on the coupling strength parameter between dark energy and dark matter. However, the GW170817 Hubble constant measurement is found to be more conservative than the Cepheid variables measurement, and in a better agreement with the current high redshift cosmological data sets. Thus, forthcoming gravitational-wave standard siren measurements of the Hubble constant would be paramount for our understanding of the dark cosmic sector.