Cosmography with bright and Love sirens

Abstract: Precision cosmology is crucial to understand the different energy components in the Universe and their evolution through cosmic time. Gravitational wave sources are standard sirens that can accurately map out distances in the Universe. Together with the source redshift information, we can then probe the expansion history of the Universe. We explore the capabilities of various gravitational-wave detector networks to constrain different cosmological models while employing separate waveform models for inspiral and post-merger part of the gravitational wave signal from equal mass binary neutron stars. We consider two different avenues to measure the redshift of a gravitational-wave source: first, we examine an electromagnetic measurement of the redshift via either a kilonova or a gamma ray burst detection following a binary neutron star merger (the electromagnetic counterpart method); second, we estimate the redshift from the gravitational-wave signal itself from the adiabatic tides between the component stars characterized by the tidal Love number, to provide a second mass-scale and break the mass-redshift degeneracy (the counterpart-less method). We find that the electromagnetic counterpart method is better suited to measure the Hubble constant while the counterpart-less method places more stringent bounds on other cosmological parameters. In the era of next-generation gravitational-wave detector networks, both methods achieve sub-percent measurement of the Hubble constant $H_0$ after one year of observations. The dark matter energy density parameter $\Omega_{\rm M}$ in the $\Lambda$CDM model can be measured at percent-level precision using the counterpart method, whereas the counterpart-less method achieves sub-percent precision. We, however, do not find the postmerger signal to contribute significantly to these precision measurements.