Combining chirp mass, luminosity distance and sky localisation from gravitational wave events to detect the cosmic dipole

Understand

A key test of the isotropy of the Universe on large scales consists in comparing the dipole in the Cosmic Microwave Background (CMB) temperature with the dipole in the distribution of sources at low redshift.

• Current analyses find a dipole in the number counts of quasars and radio sources that is 2-5 times larger than expected from the CMB, leading to a tension reaching 5$\sigma$.
• In this paper, we derive a consistent framework to measure the dipole independently from gravitational wave (GW) detections.
• We exploit the fact that the observer velocity does not only change the distribution of events in the sky, but also the luminosity distance and redshifted chirp mass, that can be extracted from the GW waveform.