No evidence for a dependence of the mass size relation of early-type
  galaxies on environment in the local Universe
  The early--type galaxy (ETG) mass--size relation has been largely studied to
understand how these galaxies have assembled their mass. One key observational
result of the last years is that massive galaxies increased their size by a
factor of a few at fixed stellar mass from $z\sim2$. Hierarchical models favor
minor mergers as a plausible driver of this size growth. Some of these models,
predict a significant environmental dependence in the sense that galaxies
residing in more massive halos tend to be larger than galaxies in lower mass
halos, at fixed stellar mass and redshift. At present, observational results of
this environmental dependence have been contradictory. In this paper we revisit
this issue in the local Universe, by investigating how the sizes of massive
ETGs depend on large-scale environment using an updated and accurate sample of
ETGs in different environments - field, group, clusters - from the Sloan
Digital Sky Survey DR7. Our analysis does not show any significant
environmental dependence of the sizes of central and satellites ETGs at fixed
stellar mass at $z\sim0$. The size-mass relation of early-type galaxies at
$z\sim0$ seems to be universal, i.e., independent of the mass of the host halo
and of the position of the galaxy in that halo (central or satellite). The
result is robust to different galaxy selections based on star formation,
morphology or central density. In fact, considering our observational errors
and the size of the sample, any size ratio larger than $30-40%$ between massive
galaxies ($log(M_*/M_\odot)>11$) living in clusters and in the field can be
ruled out at $3\sigma$ level.
