protogroups

protogroups

1. plural of protogroup
   • 2015, P. Medvedev, S. Sazonov, M. Gilfanov, “Helium diffusion during formation of the first galaxies”, in arXiv‎:

     Even stronger abundance enhancements, ${\displaystyle \delta Y_{p}/Y_{p}}$ ~ a few ${\displaystyle 10^{-3}}$, may arise at much later, post-reionization epochs, z ~ 2, in protogroups of galaxies (${\displaystyle \sim 10^{13}M_{\odot }}$) as a result of accretion of warm-hot intergalactic medium with T ~ 10^6 K.