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Researchers have demonstrated a novel method to constrain the Hubble constant using the dispersion measure distribution of 2,124 unlocalized fast radio bursts from the CHIME Catalog II, obtaining a value of 69 (+17/-15) km/s/Mpc with approximately 22% uncertainty. Unlike previous approaches that require precise redshift measurements from localized FRBs, this technique exploits how cosmic expansion affects the distribution of dispersion measures in the much larger sample of unlocalized bursts. The study shows that resolving degeneracies between the Hubble constant and FRB spectral properties could reduce the uncertainty to 9%, and combining this approach with localized FRB data could provide even tighter constraints.
Why it matters
This work opens a new avenue for addressing the Hubble tension—the discrepancy between different measurements of the universe's expansion rate—by utilizing the abundant population of unlocalized FRBs rather than relying solely on the limited sample of localized events with known redshifts. The method could become increasingly valuable as FRB catalogs grow, potentially providing independent verification of cosmological parameters.
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⚠️ Preprint – Noch nicht peer-reviewed
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Abstract: We present constraints on the Hubble constant ($H_0$) derived from the observed dispersion measure (DM) distribution of unlocalized fast radio bursts (FRBs). While localized FRBs with redshift measurements have been used to investigate the Hubble tension, their sample remains limited. Here we demonstrate that unlocalized FRBs—which are far more numerous—can independently constrain $H_0$ without requiring redshift information, as cosmic expansion imprints itself on their DM distribution. Analyzing a selected sample of 2124 unlocalized FRBs from the CHIME Catalog II, we obtain $H_0 = 69^{+17}_{-15}~mathrm{km,s^{-1},Mpc^{-1}}$ at the $1sigma$ confidence level, corresponding to an uncertainty of about 22%. Disentangling the parametric degeneracy among $H_0$, the FRB spectral index $alpha$, and the characteristic cutoff energy $E_*$ of the FRB energy distribution would reduce the fractional uncertainty in $H_0$ to 9%. This work constitutes the first $H_0$ measurement derived solely from the DM distribution of unlocalized FRBs, highlighting their potential as a new cosmological probe. Future joint analyses with localized FRBs promise even tighter constraints.
Source: Dispersion Measure Distribution of Unlocalized Fast Radio Bursts as a Probe of the Hubble Constant