Cosmological Constraints from GW-FRB Associations without Redshift Measurements for LIGO-Virgo and Cosmic Explorer

Abstract

The potential association between gravitational waves (GWs) and fast radio bursts (FRBs) offers a unique multi-messenger probe for cosmology. In this paper, we develop a redshift-independent framework to constrain cosmological parameters using the luminosity distance - dispersion measure relation, accounting for realistic astrophysical uncertainties. We perform a comprehensive comparative analysis across different GWs detector sensitivities and modeling assumptions. Specifically, we investigate the performance of the current LIGO-Virgo (LV) network (at $z < 0.2$) versus the future Cosmic Explorer (CE). Our study further evaluates the impact of different dispersion measure (DM) distributions -- specifically the corrected Macquart's PDF (Zhuge+2025) and the log-normal distribution -- and explores the influence of including or excluding host galaxy DM contributions. Using realistic simulated observations, we find that while the current LV network lacks the precision to provide meaningful constraints, CE will enable high-precision cosmology. Even without spectroscopic redshifts, CE observations can effectively break parameter degeneracies and robustly constrain both cosmology and host galaxy parameters. These results highlight the necessity of next-generation detectors.

Figures (9)

• Figure 1: Luminosity distance likelihoods for simulated NSBH GWs events, for a LV network (left) and for a CE detector (right). All of the distributions were normalised so that they have the same maximum height. Their widths are used to estimate how the $D_L$ uncertainty scales with redshift.
• Figure 2: Simulated GWs and FRBs events as a function of redshift ($z<0.2$). (Left) GWs luminosity distance, observed by LV or CE. (Center) FRBs diffuse dispersion measure, ${\rm DM}_{\rm diff}$. In this case, we assume that one is able to remove any other contributions to the ${\rm DM}$ and keep only the cosmological ones. (Right) FRBs extra galactic dispersion measure, ${\rm DM}_{\rm ext}$. The latter involves cosmological and host galaxy contributions. For fiducial testing, we generate $N=50$ events.
• Figure 3: Simulated GWs and FRBs events as a function of redshift ($0.2<z<2$). (Left) GWs luminosity distance, observed by or CE. (Center) FRBs diffuse dispersion measure, ${\rm DM}_{\rm diff}$. In this case, we assume that one is able to remove any other contributions to the ${\rm DM}$ and keep only the cosmological ones. (Right) FRBs extra galactic dispersion measure, ${\rm DM}_{\rm ext}$. The latter involves cosmological and host galaxy contributions. For fiducial testing, we generate $N=50$ events.
• Figure 4: Joint constraints on cosmological and host galaxy parameters for low-redshifts ($z<0.2$). The lower-left panels display the results obtained using the $(D_L, {\rm DM}_{\rm ext})$ dataset, while the upper-right panels show the constraints from the $(D_L, {\rm DM}_{\rm diff})$ dataset. The blue contours represent the constraints from the CE network, while the orange contours correspond to the LV network. Solid black lines indicate the input values from Planck18Planck_Cosmo_param_2018.
• Figure 5: Joint constraints on cosmological and host galaxy parameters for high-redshift case ($0.2<z<2.0$). The lower-left panels display the results obtained using the $(D_L, {\rm DM}_{\rm ext})$ dataset, while the upper-right panels show the constraints from the $(D_L, {\rm DM}_{\rm diff})$ dataset. The blue contours represent results obtained using Zhuge+2025 PDF Macquart_relation_2020, as corrected by FRBcosmo_localised_Zhuge_et_al_2025, while the orange contours correspond to the log-normal distribution. Solid black lines indicate the input values from Planck18Planck_Cosmo_param_2018.