A measurement of circumgalactic gas around nearby galaxies using fast radio bursts

Understand

The distribution of gas in the circumgalactic medium (CGM) of galaxies of all types is poorly constrained.

• Foreground CGMs contribute an extra amount to the dispersion measure (DM) of fast radio bursts (FRB).
• We measure this DM excess for the CGMs of $10^{11}-10^{13}\ M_\odot$ halos using the CHIME/FRB first data release, a halo mass range that is challenging to probe in any other way.
• Because of the uncertainty in the FRBs' angular coordinates, only for nearby galaxies is the localization sufficient to confidently associate them with intersecting any foreground halo.