New measurements of the gas fraction in galaxies and groups with the kinematic Sunyaev-Zel'dovich effect and CMB lensing

          @misc{ pirsa_PIRSA:25070035,
            doi = {10.48660/25070035},
            url = {https://pirsa.org/25070035},
            author = {Hadzhiyska, Boryana},
            keywords = {Cosmology},
            language = {en},
            title = {New measurements of the gas fraction in galaxies and groups with the kinematic Sunyaev-Zel{\textquoteright}dovich effect and CMB lensing},
            publisher = {Perimeter Institute},
            year = {2025},
            month = {jul},
            note = {PIRSA:25070035 see, \url{https://pirsa.org}}
          }
          

Abstract

I will present new constraints on the halo masses and gas fractions of DESI galaxy groups via cross-correlations with the ACT DR6 CMB lensing map. This lensing-based calibration addresses a key uncertainty in interpreting kSZ measurements: the underlying halo mass distribution and allows us to estimate the amount by which baryons have been redistributed relative to the dark matter. Our results indicate that while baryons trace dark matter on large scales, the gas is significantly more extended, with cumulative gas fractions falling well below predictions from hydrodynamical simulations like TNG300. These discrepancies, seen at 4σ significance or higher, point to strong feedback processes in the real Universe. I will also highlight the excellent agreement between our lensing-based gas fraction measurements and recent results from X-rays, and discuss the implications for modeling feedback, galaxy formation, and baryon cycling in halos.