Probing baryonic feedback with fast radio bursts: joint analyses with cosmic shear and galaxy clustering

TL;DR

Baryonic feedback introduces significant biases in weak-lensing cosmology, especially on small scales. The authors develop a multi-tracer framework combining weak lensing, FRB dispersion measures, and galaxy clustering to calibrate baryonic physics via angular power spectra computed in the halo model, including analytic marginalization of key systematics. They find that FRB DMs, when combined with WL in a $3\times2$-point analysis, substantially reduce the degradation of $S_8$ due to baryonic uncertainties and can tighten constraints on the Hubble parameter $h$, while degeneracies between baryon parameters $\log_{10} M_{\rm c}$ and $\eta_{\rm b}$ are alleviated by WL; tomography of FRBs provides limited gains. Extending to a $6\times2$-point analysis with GC improves constraints on $\Omega_m$ and $\log_{10} M_{\rm c}$ but does not further enhance $S_8$ beyond the WL+FRB combination. The study highlights the complementary role of FRBs as tracers of diffuse baryons and their potential to unlock robust, small-scale cosmology in the era of precision surveys, with future FRB samples poised to fully recover the information content of WL measurements.

Abstract

Cosmological inference from weak lensing (WL) surveys is increasingly limited by uncertainties in baryonic physics, which suppress the non-linear matter power spectrum on small scales. Multi-probe analyses that incorporate complementary tracers of the gas distribution around haloes offer a pathway to calibrate these effects and recover unbiased cosmological information. In this work, we forecast the constraining power of a joint analysis combining fiducial data from a Stage-IV WL survey with measurements of the dispersion measure from fast radio bursts (FRBs). We evaluate the ability of this approach to simultaneously constrain cosmological parameters and the astrophysical processes governing baryonic feedback, and we quantify the impact of key FRB systematics, including redshift uncertainties and source clustering. We find that, even after accounting for these effects, a 3$\times$2-point analysis of WL and FRBs significantly improves cosmological constraints, reducing the degradation factor on $S_8$ by $\sim 80\%$ compared to WL alone. We further show that FRBs alone are sensitive only to a degenerate combination of the key baryonic parameters, $\log_{10} M_{\rm c}$ and $η_{\rm b}$, and that the inclusion of WL measurements breaks this degeneracy. Finally, we extend our framework to incorporate galaxy clustering measurements using Luminous Red Galaxy and Emission Line Galaxy samples, performing a unified 6$\times$2-point analysis of WL, dispersion measures of FRBs, and galaxy clustering. While this combined approach tightens constraints on $Ω_{\rm m}$ and $\log_{10} M_{\rm c}$, it does not lead to a significant improvement in $S_8$ constraints beyond those obtained from WL and FRBs alone.

Figures (10)

• Figure 1: The contributions to the angular power spectrum arising from FRB source clustering effects. The bands corresponding to the correlations involving the source-clustering term represent the range $b_{\rm f} \in \{1.0, 3.0\}$ for the FRB bias. Left Panel. Components of the FRB auto-correlation, $C_{\ell}^{\mathcal{DD}}$, as given in Eq. \ref{['eq:Cl_DD']}. Middle Panel. Components of the cross-correlation between the FRB DM and the first WL redshift bin, $C_{\ell}^{\mathcal{D}\gamma}$, from Eq. \ref{['eq:Cl_Dgamma']}. Right Panel. Components of the cross-correlation between the FRB DM and galaxy clustering for the LRG sample, $C_{\ell}^{\mathcal{D}\rm g}$, from Eq. \ref{['eq:Cl_Dg']}.
• Figure 2: The signal-to-noise ratio, SNR, as a function of the maximum multipole, $\ell_{\rm max}$, for two FRB number densities. The left panel shows the SNR of the FRB auto-angular power spectrum, while the right panel shows the SNR of the FRB--WL cross-angular power spectrum for the first (dashed) and the final (solid) WL redshift bins. The red curves correspond to the fiducial case with $\bar{n} = 0.5 \; \mathrm{deg}^{-2}$, and the blue curves to a future survey with $\bar{n} = 5.0 \; \mathrm{deg}^{-2}$. The vertical dashed vertical lines indicate the adopted maximum scale cuts, $\ell^{{\cal D}{\cal D}}_{\rm max} = 500$ and $\ell^{{\cal D}\gamma}_{\rm max}=1000$.
• Figure 3: The marginalised posteriors on cosmological parameters for LSST-like weak lensing data only for fixed baryonic parameters (solid black), LSST-like weak lensing data only with marginalisation over baryonic parameters (dashed black), and a joint analysis of LSST-like weak lensing data with FRB DM correlations in a 3$\times$2-point analysis (blue). The inner and outer contours show the 68 per cent and 95 per cent confidence levels, respectively. We marginalise over intrinsic alignments, photometric redshift uncertainties, and multiplicative shape biases for the weak lensing data. We include multipoles up to $\ell_{\rm max} = \{500, 1000, 2000\}$ for the FRB auto-correlations, WL--FRB cross-correlations, and WL auto- and cross-correlations, respectively.
• Figure 4: The impact of varying the parameters $h$, $\log_{10} M_{\rm c}$, and $\eta_{\rm b}$ on the $C_{\ell}^{\mathcal{DD}}$ (top) and $C_{\ell}^{\mathcal{D}\gamma}$ (bottom) angular power spectra. Each column isolates the response to a single parameter by varying it around the fiducial model, while keeping the remaining parameters fixed at their fiducial values.
• Figure 5: The marginalised posteriors on $\log_{10} M_{\rm c}$ and $\eta_{\rm b}$ for three different probes of baryonic physics with fixed cosmological parameters. The blue, purple, and red contours correspond to the constraints obtained from FRB DMs alone, kSZ alone, and X-rays alone, respectively. The inner and outer contours show the 68 per cent and 95 per cent confidence levels, respectively. The mock measurements of X-ray gas fractions are based on a sample of 5259 clusters from the eROSITA dataset, and the mock measurements of the stacked kSZ profile assume a CMB-S4-like experiment.