A preprint released in April 2026 by Kritti Sharma, Elisabeth Krause and collaborators (arXiv:2604.22105) represents a major advance in observational cosmology. Using 3,455 fast radio bursts (FRBs) detected by the CHIME/FRB telescope with roughly 15-arcminute localizations, the team measured statistically significant cross-correlations (2.6–5.0σ) between FRB dispersion measures (DMs) and ten different tracers of large-scale structure and baryonic gas out to redshift z≈1.5. These tracers include galaxy catalogs, weak gravitational lensing, cosmic infrared background, CMB lensing, the thermal Sunyaev-Zel’dovich effect, X-ray emission from clusters and superclusters, the soft X-ray background, and radio continuum.

Methodologically, the authors stack the DMs against these maps rather than relying on precise host-galaxy redshifts for each burst. The coarse angular resolution means the work is inherently statistical: it cannot trace individual filaments but instead reveals that sightlines passing through overdense regions carry systematically higher electron columns. This is exactly what is predicted if the “missing baryons” — ordinary matter not yet accounted for in stars, galaxies, or the warm-hot intergalactic medium — reside in the tenuous filaments of the cosmic web.

The study builds on but significantly expands earlier work. Macquart et al. (Nature, 2020; arXiv:2005.13161) used a much smaller sample of precisely localized FRBs to demonstrate that the integrated DM–redshift relation matches the baryon density expected from Big Bang nucleosynthesis and the cosmic microwave background. Later hydrodynamic simulations (e.g., IllustrisTNG and BAHAMAS) predicted how feedback from supernovae and active galactic nuclei should redistribute those baryons. What the new anthology adds is a multi-tracer consistency check across different gas phases: cool, warm, and hot. Previous single-tracer studies often missed this cross-validation; many early FRB–galaxy correlation papers, for instance, could not distinguish whether excess DM arose from galactic halos or truly intergalactic filaments.

The preprint’s most striking result is its leverage on feedback physics. The measured amplitudes of DM–tSZ and DM–soft-X-ray-background correlations align, at the 0.5σ level, with moderate-feedback models. A “weak feedback” scenario, in which gas is not efficiently ejected from galaxies, is excluded at 3.5σ by the soft X-ray data. This is a genuine cosmological insight: the amount of baryonic matter locked in hot halos versus dispersed in filaments directly affects predictions for galaxy formation efficiency and the thermal history of the universe.

Limitations must be clearly stated. At 15-arcminute localization, the analysis cannot yet produce tomographic maps of individual structures; it remains a statistical power spectrum–style measurement. The sample is confined to z ≲ 1.5, and systematic uncertainties in tracer maps (especially X-ray backgrounds) could shift the inferred feedback strength. Because this is a preprint, not yet peer-reviewed, independent teams should scrutinize the foreground subtraction and covariance modeling.

Taken together with upcoming facilities — BURSTT, CHORD, DSA-2000, and eventually the SKA — the toolkit demonstrated here illuminates one of cosmology’s longest-standing gaps. We have mapped dark matter via weak lensing with exquisite precision; ordinary baryons have remained elusive precisely because they are diffuse and multi-phase. By treating FRBs as backlights that illuminate every ionized electron along the line of sight, independent of temperature, astronomers now possess a quantitative, multi-probe route to complete the cosmic baryon census. The patterns revealed — stronger DM in overdense environments, consistency with moderate feedback — match expectations from structure-formation simulations yet close an observational loophole that single-tracer studies left open. This work therefore marks the transition from proof-of-concept FRB cosmology to precision mapping of the cosmic web.