摘要：Aims. The aim of this work is twofold: first, to assess whether the population of elliptical galaxies in cluster at z ~ 1.3 differs from the population in the field and whether their intrinsic structure depends on the environment where they belong; second, to constrain their properties 9 Gyr back in time through the study of their scaling relations.
Methods. We compared a sample of 56 cluster elliptical galaxies selected from three clusters at 1.2 2 × 1011M⊙) and large (Re> 4−5 kpc) elliptical galaxies with respect to the cluster. Nonetheless, at ℳ∗< 2 × 1011M⊙, the two populations are similar. The size-mass relation of cluster and field ellipticals at z ~ 1.3 clearly defines two different regimes, above and below a transition mass mt ≃ 2−3 × 1010M⊙: at lower masses the relation is nearly flat (Re ∝ Μ*-0.1±0.2), the mean radius is nearly constant at ~1 kpc and, consequenly, ΣRe ≃ Σ1 kpc while, at larger masses, the relation is Re ∝ Μ*0.64±0.09. The transition mass marks the mass at which galaxies reach the maximum stellar mass density. Also the Σ1 kpc-mass relation follows two different regimes, above and below the transition mass (Σ1 kpc ∝ Μ*1.070.64>mt) defining a transition mass density Σ1 kpc ≃ 2−3 × 103M⊙ pc-2. The effective stellar mass density ΣRe does not correlate with mass; dense/compact galaxies can be assembled over a wide mass regime, independently of the environment. The central stellar mass density, Σ1 kpc, besides being correlated with the mass, is correlated to the age of the stellar population: the higher the central stellar mass density, the higher the mass, the older the age of the stellar population.
Conclusions. While we found some evidence of environmental effects on the elliptical galaxies as a population, we did not find differences between the intrinsic properties of cluster and field elliptical galaxies at comparable redshift. The structure and the shaping of elliptical galaxies at z ~ 1.3 do not depend on the environment. However, a dense environment seems to be more efficient in assembling high-mass large ellipticals, much rarer in the field at this redshift. The correlation found between the central stellar mass density and the age of the galaxies beside the mass shows the close connection of the central regions to the main phases of mass growth.
关键词：galaxies: elliptical and lenticular, cD;galaxies: evolution;galaxies: clusters: general;galaxies: high-redshift;galaxies: formation
