MASSIVE NEUTRINOS PROMOTE THE SIZE GROWTH OF EARLY-TYPE GALAXIES.

The effect of massive neutrinos on the evolution of early-type galaxies in size and stellar mass is explored by tracing the merging history of galaxy progenitors with the help of robust semi-analytic prescriptions. We show that as the presence of massive neutrinos plays a role in enhancing the mean merger rate per halo as well as the merger-driven increment in halo mass, the high-z progenitors of a massive descendant galactic halo evolve more rapidly in mass-normalized size for a ⋀MDM (⋀ cold dark matter + massive neutrinos) model than for the ⋀CDM (⋀ cold dark matter) case. We provide a physical reason for why the halo mass growth rate and the merger rate are higher in a ⋀MDM cosmology and conclude that if the presence and the role of massive neutrinos are properly taken into account, then it may explain the anomalous compactness of the high-z massive ETGs compared with local giant ellipticals with similar stellar masses. [ABSTRACT FROM AUTHOR]