Precise peculiar velocities from gravitational waves accompanied by electromagnetic signals and cosmological applications

Understand

Peculiar velocities are a precious tool to study the large-scale distribution of matter in the local universe and test cosmological models.

• However, present measurements of peculiar velocities are based on empirical distance indicators, which introduce large error bars.
• Here we present a new method to measure the peculiar velocities, by directly estimating luminosity distances through waveform signals from inspiralling compact binaries and measuring redshifts from electromagnetic (EM) counterparts.
• In the future, with the distance uncertainty of GW events reducing to $0.1$ per cent by future GW detectors, the uncertainty of the peculiar velocity can be reduced to $10$ km/s at 100 mega parsecs.