Massive Neutrinos Promote the Size Growth of Early-Type Galaxies
  The effect of massive neutrinos on the evolution of the early type galaxies
(ETGs) in size ($R_{e}$) and stellar mass ($M_{\star}$) is explored by tracing
the merging history of galaxy progenitors with the help of the robust
semi-analytic prescriptions. We show that as the presence of massive neutrinos
plays a role of enhancing the mean merger rate per halo, the high-$z$
progenitors of a descendant galaxy with fixed mass evolves much more rapidly in
size for a $\Lambda$MDM ($\Lambda$CDM + massive neutrinos) model than for the
$\Lambda$CDM case. The mass-normalized size evolution of the progenitor
galaxies, $R_{e}[M_{\star}/(10^{11}M_{\odot})]^{-0.57}\propto (1+z)^{-\beta}$,
is found to be quite steep with the power-law index of $\beta\sim 1.5$ when the
neutrino mass fraction is $f_{\nu}=0.05$, while it is $\beta\sim 1$ when
$f_{\nu}=0$. It is concluded that if the presence and role of massive neutrinos
are properly taken into account, it may explain away the anomalous compactness
of the high-$z$ ETGs compared with the local ellipticals with similar stellar
masses.
