Measuring the circum- and inter-galactic baryon contents with fast radio bursts

Understand

Over 80% of the cosmic baryon density is likely to be distributed in the diffuse, $\gtrsim10^{4}$ K circum- and inter-galactic medium (CGM and IGM respectively).

• We demonstrate that the dispersion measures (DMs) of samples of localized Fast Radio Bursts (FRBs) can be used to measure the distribution of baryons between the CGM and IGM.
• We propose to separate the CGM and IGM contributions to FRB DMs by including redshift and mass measurements of intervening galaxies.
• Using simulated samples of FRB sightlines through intervening galaxy halos and an illustrative model for the CGM, and including realistic observational uncertainties, we show that small samples ($O(10^{1})-O(10^{2})$) of localized FRBs are sensitive to the presence of CGM gas.