Ray-tracing Fast Radio Bursts Through IllustrisTNG: Cosmological Dispersion Measures from Redshift 0 to 5.5
- 1Center for Astrophysics ∣ Harvard & Smithsonian
- 2Max-Planck-Institut für Astrophysik
Abstract
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 has started to empirically constrain the distribution of cosmic baryons, making it crucial to accurately forward model their propagation within cosmological simulations. In this work, we 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 full-sky DM maps observed from Milky Way–like environments. 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%. We show that our results are consistent with the most recent observational data from the DSA-110, ASKAP, and CHIME. We offer a 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. We find that using simulation box sizes of or below 35 h ⁻¹ Mpc, or low resolutions with baryonic masses exceeding 5 × 10 ⁸ h ⁻¹ M ⊙ , can distort the derived DM signal by more than 8%. Our findings provide new insights into how the cosmic web shapes FRB signals and highlight the importance of accurate methodology when comparing cosmological simulations against observations.
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BibTeX
@article{konietzka2026raytracing,
title = {{Ray-tracing Fast Radio Bursts Through IllustrisTNG: Cosmological Dispersion Measures from Redshift 0 to 5.5}},
author = {Ralf M. Konietzka and Liam Connor and Vadim A. Semenov and Angus Beane and Volker Springel and Lars Hernquist},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/ae99e8},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae99e8},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Ray-tracing Fast Radio Bursts Through IllustrisTNG: Cosmological Dispersion Measures from Redshift 0 to 5.5
AU - Ralf M. Konietzka
AU - Liam Connor
AU - Vadim A. Semenov
AU - Angus Beane
AU - Volker Springel
AU - Lars Hernquist
PY - 2026
DA - 2026/10/12
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae99e8
UR - https://iopscience.iop.org/article/10.3847/1538-4357/ae99e8
AB - 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 has started to empirically constrain the distribution of cosmic baryons, making it crucial to accurately forward model their propagation within cosmological simulations. In this work, we 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 full-sky DM maps observed from Milky Way–like environments. 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%. We show that our results are consistent with the most recent observational data from the DSA-110, ASKAP, and CHIME. We offer a 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. We find that using simulation box sizes of or below 35 h ⁻¹ Mpc, or low resolutions with baryonic masses exceeding 5 × 10 ⁸ h ⁻¹ M ⊙ , can distort the derived DM signal by more than 8%. Our findings provide new insights into how the cosmic web shapes FRB signals and highlight the importance of accurate methodology when comparing cosmological simulations against observations.
SN - 0004-637X
SN - 1538-4357
ER -