Description
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, providing new, stringent tests of AGN feedback models implemented in cosmological simulations.
In this talk, I present a novel forward-modeling framework for measuring FRB DMs in IllustrisTNG that continuously traces rays through the simulation while reconstructing all traversed line segments within the underlying Voronoi mesh.
This approach overcomes a key limitation of previous TNG-based studies, in which a sparse snapshot sampling in the path integral leads to a systematic misestimation of the variance and higher-order moments of the DM distribution by over 50%.
By confronting our simulated FRB catalogs with recent observations from DSA-110, ASKAP, and CHIME, we quantify the distribution of baryons relative to the underlying matter, allowing us to place new constraints on the efficiency and large-scale impact of AGN feedback. We find that neither the momentum-driven AGN feedback model in IllustrisTNG nor the thermal bubble feedback implementation in the original Illustris simulation can reproduce the observed FRB DM signal, pointing to the need for next-generation AGN implementations capable of redistributing baryons in a manner consistent with observations.
Our results add to the growing body of evidence from probes such as the kSZ effect and X-ray observations, indicating a significant tension between simulations and the observed baryon distribution, and highlight the power of FRBs as a new, independent probe of AGN feedback.