Lynch: What’s the matter with Σm_ν? / Ried: Backlighting extended gas halos around luminous red galaxies: kinematic Sunyaev-Zel'dovich effect from DESI Y1 x ACT

Speaker: Gabriel Lynch (UC Davis) / Berni Reid (KIPAC) In Person and zoom 

Zoom info: https://stanford.zoom.us/j/98604058568

Lynch: Due to non-zero neutrino rest masses we expect the energy density today in non-relativistic matter, ωm, to be greater than the sum of baryon and cold dark matter densities, ωcb. We also expect the amplitude of deflections of CMB photons due to gravitational lensing to be suppressed relative to expectations assuming massless neutrinos. The combination of CMB and BAO data, however, appear to be defying both of these expectations. I will review how the neutrino rest mass is determined from cosmological observations, and emphasize the complementary roles played by BAO and lensing data in this process. I will then introduce a phenomenological “negative neutrino mass” model to show that CMB and BAO data have a 3 σ preference forωm being less than expected from the CMB alone (assuming the minimal sum of neutrino masses allowed by oscillation experiments).