Wavelet-Scattering Signatures of Fuzzy Dark Matter in Simulated 21 cm Brightness-Temperature Maps

Abstract

We study the effect of fuzzy dark matter (FDM) on the multiscale morphology of simulated redshifted 21\,cm maps during Cosmic Dawn and the Epoch of Reionization. Using FDM-modified \texttt{21cmFAST} light cones, we apply the two-dimensional wavelet scattering transform (WST) to matched 2\,MHz map products. The first-order coefficients $S_1(j)$ summarize wavelet-band amplitudes, while the normalized second-order ratio $R=S_2/S_1(j_1)$ measures ordered cross-scale modulation. FDM shifts and reshapes both summaries through delayed halo and source formation. We compare a two-dimensional power spectrum (PS), WST, and their combination on the same transferred and noisy maps. In this controlled local Fisher analysis, PS+WST reduces the marginalized errors on the FDM mass, effective X-ray emissivity normalization, and ionizing efficiency by approximately a factor of 1.8 relative to the matched two-dimensional PS baseline, although the dominant mass-heating degeneracy remains. An idealized three-wedge test shows that $R$ is less reshaped at the coefficient level than $S_1$. The covariance includes thermal noise conditional on one fiducial light cone but not cosmic variance or foreground residuals; the results are therefore relative information comparisons, not survey forecasts or a demonstration of superiority over a full three-dimensional PS analysis.