Constraining cosmological parameters from strong lensing with DECIGO and B-DECIGO sources

TL;DR

This paper explores how future gravitational wave observations from DECIGO and B-DECIGO can constrain cosmological parameters like matter density and Hubble constant through lensing statistics and time delay methods.

Contribution

It demonstrates the potential of space-borne gravitational wave detectors to provide competitive constraints on cosmological parameters using lensing data.

Findings

DECIGO can constrain Ω_M to 0.288–0.314.

H_0 can be measured with 3–11% accuracy at 5σ.

B-DECIGO offers less precise constraints than DECIGO.

Abstract

Gravitational lensing has long been used to measure or constrain cosmology models. Although the lensing effect of gravitational waves has not been observed by LIGO/Virgo, it is expected that there can be a few to a few hundreds lensed events to be detected by the future Japanese space-borne interferometers DECIGO and B-DECIGO, if they are running for 4 years. Given the predicted lensed gravitational wave events, one can estimate the constraints on the cosmological parameters via the lensing statistics and the time delay methods. With the lensing statistics method, the knowledge of the lens redshifts, even with the moderate uncertainty, will set the tight bound on the energy density parameter $\Omega_M$ for matter, that is, $0.288\lesssim\Omega_M\lesssim0.314$ at best. The constraint on the Hubble constant $H_0$ can be determined using the time delay method. It is found out that at $5\sigma$, $|\delta H_0|/H_0$ ranges from $3\%$ to $11\%$ for DECIGO, and B-DECIGO will give less constrained results, $8\%-15\%$. In this work, the uncertainties on the luminosity distance and the time delay distance are set to be $10\%$ and $20\%$, respectively. The improvement on measuring these distances will tighten the bounds.