A Hydrodynamical Simulations-based Model that Connects the FRB DM–Redshift Relation to Suppression of the Matter Power Spectrum via Feedback

Abstract

Understanding the impact of baryonic feedback on the small-scale ( k ≳ 1 h Mpc ^−1 ) matter power spectrum is a key astrophysical challenge, and essential for interpreting data from upcoming weak-lensing surveys, which require percent-level accuracy to fully harness their potential. Astrophysical probes, such as the kinematic and thermal Sunyaev–Zel’dovich effects, have been used to constrain feedback at large scales ( k ≲ 5 h Mpc ^−1 ). The sightline-to-sightline variance in the fast radio bursts (FRBs) dispersion measure (DM) correlates with the strength of baryonic feedback and offers unique sensitivity at scales up to k ∼ 10 h Mpc ^−1 . We develop a new simulation-based formalism in which we parameterize the distribution of DM at a given redshift, p (DM∣ z ), as a log-normal with its first two moments computed analytically in terms of cosmological parameters and the feedback-dependent electron power spectrum P _ee ( k , z ). We find that the log-normal parameterization provides an improved description of the p (DM∣ z ) distribution observed in hydrodynamical simulations as compared to the standard F -parameterization. Our model robustly captures the baryonic feedback effects across a wide range of baryonic feedback prescriptions in hydrodynamical simulations, including IllustrisTNG , SIMBA , and Astrid . Leveraging simulations incorporates the redshift evolution of the DM variance by construction and facilitates the translation of constrained feedback parameters to the suppression of matter power spectrum relative to gravity-only simulations. We show that with 10 ^4 FRBs, the suppression can be constrained to percent-level precision at large scales and ∼10% precision at scales k ≳ 10 h Mpc ^−1 with prior-to-posterior 1 σ constraint width ratio ≳20.

Keywords

• Observational cosmology
• Radio transient sources