Abstract

Fast radio bursts (FRBs) are frequent, bright millisecond bursts of radio emission that have fortunately (unfortunately) turned out to not be from microwave ovens (alien light sails), but rather to be some extragalactic phenomenon likely associated with magnetars Radio astronomers are beginning to localize these bursts to specific galaxies, opening up new extragalactic observables — the bursts’ dispersion, scattering, and Faraday rotation. Dispersion in particular yields the intervening column of electrons, providing a unique tool to probe the 95% of the baryons that sit outside of galaxies (the vast majority of which are invisible using other observational methods). I will present the first applications of FRB diffuse baryon science, featuring results from the commensal real-time ASKAP fast-transients (CRAFT) survey. Even with just a handful of well-localized bursts, we are able to make interesting inferences about circumgalactic gas and the “missing baryons”. I may end with an idea for part-in-a-thousand-level precision cosmology with FRBs that may only be a little crazy.