Critical Stellar Central Densities Drive Galaxy Quenching in the Nearby
  Universe
  We study the structural and environmental dependence of the star formation on
the plane of stellar mass versus central core density ($\Sigma_{\rm 1\ kpc}$)
in the nearby universe. We study the central galaxies in the sparse environment
and find a characteristic population-averaged $\rm \Sigma_{1\ kpc} \sim
10^9-10^{9.2}\ M_{\odot}\ kpc^{-2}$, above which quenching is operating. This
$\rm \Sigma^{crit}_{1\ kpc}$ only weakly depends on the stellar mass,
suggesting that the mass-quenching of the central galaxies is more closely
related to the processes that operate in the central regions than over the
entire galaxies. For satellites, at a given stellar mass, environment-quenching
appears to operate in a similar fashion as mass-quenching in centrals, also
starting from galaxies with high $\rm \Sigma_{1\ kpc}$ to low $\rm \Sigma_{1\
kpc}$, and $\rm \Sigma^{crit}_{1\ kpc}$ becomes strongly mass-dependent, in
particular in dense regions. This is because (1) more low-mass satellites are
quenched by the environmental effects in denser regions and (2) at fixed
stellar mass and environment, the environment-quenched satellites have, on
average, larger $\Sigma_{\rm 1\ kpc}$, $\rm M_{1\ kpc}/M_{\star}$ and Sersic
index $n$, and as well as smaller size. These results imply that either some
dynamical processes change the structure of the satellites during quenching or
the satellites with higher $\Sigma_{\rm 1\ kpc}$ are more susceptible to the
environmental effects.
