Fast Radio Burst Cosmology in IllustrisTNG: Simulated Dispersion Measures from Redshift 0 to 5.5

Speaker: Ralf Konietzka (Harvard/CFA) In Person and zoom 

The dispersion measures (DMs) of Fast Radio Bursts (FRBs) arise predominantly from free electrons in the large-scale structure of the Universe. The increasing number of FRB observations have started to empirically constrain the distribution of cosmic baryons, making it crucial to accurately forward model their propagation within cosmological simulations. In this talk, I present a method for measuring FRB DMs in IllustrisTNG that continuously traces rays through the simulation while reconstructing all traversed line segments within the underlying Voronoi mesh. Leveraging this technique, we create over 20 publicly available DM catalogs, including a full-sky DM map observed from a Milky Way-like environment. Our method addresses a problem in previous TNG-based studies, in which a sparse snapshot sampling in the path integral leads to a misestimation of the standard deviation and higher moments of the DM distribution p(DM|z) by over 50%.I demonstrate that our results are consistent with the most recent observational data from the DSA-110, ASKAP, and CHIME. Furthermore, I present a new functional form for p(DM|z) that provides very good fits across all redshifts from 0 to 5.5, showing that the previously proposed log-normal distribution is not well matched to the data. I will conclude by discussing how we leverage our simulated FRB catalogs to constrain the distribution of baryons relative to the underlying matter in order to quantify the strength of baryonic feedback.