Speaker
Description
Gravitational-wave observations allow us to determine source distances without external calibration. However, large localization errors limit their cosmological utility, since redshift information cannot be obtained from gravitational waves alone. Multi-messenger events, such as GW170817, enable host-galaxy identification, but such cases remain rare. The Hubble constant inferred from GW170817 is consistent with other measurements, albeit with large uncertainties. To reduce statistical errors, a much larger sample of GW sources with identified host galaxies is required.
Observations in the mid-frequency band around 0.1 Hz can substantially improve both sky localization and distance measurements. Several proposed space-based detector concepts operating in this band could localize sources within volumes smaller than those occupied by individual galaxies, enabling unique host-galaxy identification. With detectors of moderate sensitivity, the typical redshift horizon could be extended to ~0.1 for binary neutron star mergers and ~0.3 for neutron star–black hole mergers. Such capabilities would allow us to constrain key cosmological parameters with a precision comparable to that achieved by measurements of the Cosmic Microwave Background (CMB).
