Marc Huertas-Company, Francesco Shankar, Simona Mei, Mariangela Bernardi, J. A. L. Aguerri, Alan Meert, Vinu Vikram
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~2. Minor mergers have been put forward in hierarchical models 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 carefully investigating how the sizes of massive ETGs depend on large-scale environment using an updated and accurate sample of massive ETGs (>10^{11}) in different environments - field, group, clusters - from the Sloan Digital Sky Survey DR7. Observations do not show any environmental dependence of the sizes of central and satellites ETGs at fixed stellar mass. The size-mass relation of early-type galaxies 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). We compare our observational results with two hierarchical models built from the Millennium Simulation. Once observational errors are properly included in model predictions, we find our results to broadly agree (at 1-2 sigma level) with one of the models, but strongly disagree with the other (at ~3sigma level), proving how useful environment is in testing galaxy evolution models.
View original:
http://arxiv.org/abs/1212.4143
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