Model-Independent Measurements of Baryon Feedback with kSZ and Galaxy-Galaxy Lensing

Baryonic feedback introduces substantial uncertainty into cosmological inference from weak lensing. Henry Liu presents measurements of radial gas fractions around DESI galaxies that avoid assuming parametric gas profiles. The method combines galaxy-galaxy lensing with the kinematic Sunyaev–Zel’dovich effect, using a modified kSZ filter matched to the lensing delta-Sigma observable to estimate gas fractions directly.

The analysis joins DESI DR2 Bright Galaxy Survey and luminous-red-galaxy samples with ACT DR6 microwave-background maps and HSC Y3 shear data. Gas fractions are suppressed at small projected separations and approach the cosmic value farther out. A simulation-calibrated compensation for the ACT beam, designed to be independent of feedback, yields baryon-depletion detections with signal-to-noise ratios of 17.1 for BGS and 15.8 for the first LRG bin. Comparisons with Illustris, IllustrisTNG, SIMBA and FLAMINGO explore different feedback prescriptions. The talk concludes with future directions and implications for feedback and matter-power suppression.