Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts

Abstract A sample of 14 FRBs with measured redshifts and scattering times is used to assess contributions dispersion from the intergalactic medium (IGM), galaxy halos, disks host galaxies. The IGM halos contribute significantly measures (DMs) but evidently not scattering, which then dominated by This enables usage for estimating DM galaxies also a combined scattering–dispersion redshift estimator. Redshift estimation calibrated using Galactic pulsars after taking into account different geometries lines sight. DM-only estimator has bias ∼0.1 rms error ∼0.15 in estimate an assumed ad hoc value 50 pc cm −3 galaxy’s contribution. shows less factor 4 10 20%–40% smaller error. We find that values baryonic fraction ionized f igm ≃ 0.85 ± 0.05 optimize scattering. Our study suggests 2 candidate associations (FRB 20190523A FRB 20190611B) should be reconsidered.