KSZ Velocity Reconstruction with ACT and DESI-LS using a Tomographic QML Power Spectrum Estimator
We perform kinetic Sunyaev-Zel'dovich (kSZ) velocity reconstruction on data from ACT DR6 and DESI-LS DR9. To estimate the cross-power between kSZ velocity reconstruction and galaxy density, we make use of a novel quadratic maximum likelihood (QML) power spectrum estimator in redshift binned spherical coordinates. We find a detection of the kSZ signal from the cross-correlation between the estimated velocity field and the large-scale galaxy field of $10 σ$. We estimate an amplitude $A=0.42 \pm 0.042$ of the kSZ signal relative to a halo model prediction, possibly indicating strong feedback in massive halos, in agreement with previous studies. We compare the result to the pseudo-$C_{\ell}$ analysis on the same dataset, finding a $\sim$20% improvement in the SNR. Our work demonstrates the feasibility of an optimal QML analysis at the required resolution, and will be a powerful tool for kSZ cosmology with upcoming high-resolution surveys.