Calibrating the cosmic distance ladder using gravitational-wave observations

Type Ia supernovae (SNe Ia) are among the pre-eminent distance ladders for precision cosmology due to their intrinsic brightness, which allows them to be observable at high redshifts. Their usefulness as unbiased estimators of absolute cosmological distances, however, depends on accurate understanding of their intrinsic brightness, or anchoring their distance scale. This knowledge is based on calibrating their distances with Cepheids. Gravitational waves from compact binary coalescences, being standard sirens, can be used to validate distances to SNe Ia when both occur in the same galaxy or galaxy cluster. The current measurement of distance by the advanced LIGO and Virgo detector network suffers from large statistical errors (∼50%). However, we find that, using a third-generation gravitational-wave detector network, standard sirens will allow us to measure distances with an accuracy of ∼0.1%-3% for sources within ≤300 Mpc. These are much smaller than the dominant systematic error of ∼5% due to the radial peculiar velocity of host galaxies. Therefore, gravitational-wave observations could soon add a new cosmic distance ladder for an independent calibration of distances to SNe Ia.