Constraining the Baryon Fraction in the Intergalactic Medium with 92 localized Fast Radio Bursts (2506.03536v1)

Abstract: Fast radio bursts (FRBs) are emerging as powerful cosmological probes for constraining the baryon fraction in the intergalactic medium (IGM), offering a promising avenue to address the missing baryon problem. In this paper, we analyze constraints on the IGM baryon fraction ($f_\mathrm{IGM}$) using 92 localized FRBs, incorporating a corrected probability distribution function for the IGM dispersion measure within three different cosmological models. We find that variations in the underlying cosmological model have a negligible impact on the inferred values of $f_\mathrm{IGM}$. While the NE2001 Galactic electron density model yields slightly higher $f_\mathrm{IGM}$ values compared to the YMW16 model, the results are consistent within the 1$\sigma$ confidence level. Additionally, there is no statistically significant evidence for redshift evolution in $f_\mathrm{IGM}$. Our analysis constrains $f_\mathrm{IGM}$ to the range $0.8 \sim 0.9$, providing strong support for the idea in which the majority of the missing baryons reside in the diffuse IGM.