Presentation #116.28 in the session Stellar/Compact Objects.
Supernova remnants (SNRs) are considered to be the primary source of Galactic cosmic rays (CRs). However, increasing evidence shows that the winds of young massive star clusters (YMCs) may also contribute substantially to CR acceleration. In this poster, we present new results analyzing 14 years of Fermi Gamma-ray Telescope data toward 11 YMCs < 3 Myr old (where supernovae have not yet occurred) in the Milky Way. We measure the gamma-ray luminosities from these sources, and we evaluate how efficiently their winds accelerate CRs. We use these constraints to estimate the cosmic-ray density and the diffusion coefficient. These results are important inputs for CR feedback prescriptions in galaxy formation simulations.