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arXiv · 2506.03258

Exploring selection biases in FRB dispersion-galaxy cross-correlations with magnetohydrodynamical simulations

April Qiu Cheng·Shion Elizabeth Andrew·Haochen Wang·Kiyoshi W. Masui
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Abstract

The dispersion measure (DM) of fast radio bursts (FRBs) in conjunction with their redshifts can be used as powerful probes of the distribution of extragalactic plasma. With a large enough sample, the free-electron--galaxy power spectrum $P_{eg}$ can be measured by cross-correlating FRB DMs with galaxy positions. However, a precise measurement of $P_{eg}$ requires a careful investigation of selection effects: the probability of both observing the FRB DM and obtaining a host galaxy redshift depends on their properties. We ray trace through the magnetohydrodynamic simulation IllustrisTNG to investigate the impact of expected observational selection effects on FRB dispersion--galaxy angular cross-correlations with a sample of 3000 FRBs at $0.3\leq z\leq 0.4$ . Our results show that cross-correlations with such an FRB sample are robust to properties of the FRB host galaxy: this includes DM contributions from the FRB host and optical follow-up selection effects. We also find that such cross-correlations are robust to DM-dependent and scattering selection effects specific to the CHIME/FRB survey. However, a DM-dependent selection effect that cuts off the 10\% most dispersed FRBs at a fixed redshift shell can bias the amplitude of the cross-correlation signal by over 50\% at angular scales of $\sim 0.1^\circ$, corresponding to $\sim$ Mpc physical scales. Our findings highlight the importance of both measuring and accounting for selection effects present in existing FRB surveys, as well as mitigating DM-dependent selection effects in the design of upcoming FRB surveys aiming to probe large-scale structure with FRBs.

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April Qiu Cheng, Shion Elizabeth Andrew, Haochen Wang, Kiyoshi W. Masui. 2025-06-03. Exploring selection biases in FRB dispersion-galaxy cross-correlations with magnetohydrodynamical simulations. https://doi.org/10.3847/1538-4357%2Fae369f

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