Lifting Astrophysical Barriers to Small Scale Cosmology

Jared Siegel presents measurements that address two limitations of weak-lensing cosmology: intrinsic galaxy alignments and baryonic feedback. More than two million DESI galaxies and four lensing surveys provide alignment measurements across colour, luminosity, stellar mass and redshift. Combining Sunyaev–Zel’dovich profiles, eROSITA gas fractions and galaxy–galaxy lensing then constrains how feedback redistributes matter in groups and clusters at redshifts between zero and one. The results indicate stronger gas expulsion beyond virial radii than many simulations predict, reducing small-scale matter power. Incorporating these empirical constraints into cosmic-shear analyses improves cosmological inference.