Linear anisotropies in dispersion-measure-based cosmological observables

Abstract

We derive all contributions to the dispersion measure (DM) of electromagnetic pulses to linear order in cosmological perturbations, including both density fluctuations and relativistic effects. We then use this result to calculate the power spectrum of DM-based cosmological observables to linear order in perturbations. In particular, we study two cases: maps of the dispersion measure from a set of localized sources (including the effects of source clustering), and fluctuations in the density of DM-selected sources. The impact of most relativistic effects is limited to large angular scales, and is negligible for all practical applications in the context of ongoing and envisaged observational programs targeting fast radio bursts. We compare the leading contributions to DM-space clustering, including the effects of gravitational lensing, and find that the signal is dominated by the fluctuations in the free electron column density, rather than the local source clustering or lensing contributions. To compensate for the disappointing irrelevance of relativistic effects, we re-derive them in terms of the geodesic equation for massive particles in a perturbed Friedmann-Robertson-Walker metric.

Just enough pages and figures. Accepted in PRD

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Cited by in corpus (7)

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• Catalog-based pseudo-$C_{\ell }$s
• Constraints on Equivalence Principle Violation from Gamma Ray Bursts
• The halo bias for number counts on the light cone from relativistic N-body simulations
• Relativistic imprints on dispersion measure space distortions
• Exploring selection biases in FRB dispersion-galaxy cross-correlations with magnetohydrodynamical simulations
• Probing baryonic feedback with fast radio bursts: joint analyses with cosmic shear and galaxy clustering