Cluster and field elliptical galaxies at z~1.3. The marginal role of the environment and the relevance of the galaxy central regions [GA]

We compared the properties of 56 elliptical galaxies selected from three clusters at 1.2<z<1.4 with those of field galaxies at the same redshift in the GOODS-S (~30), COSMOS (~180) and CANDELS (~220) fields. We derived the relationships among effective radius, surface brightness, stellar mass, effective stellar mass density Sigma_Re and central mass density Sigma_1kpc within 1 kpc radius. We find that cluster elliptical galaxies do not differ from field ellipticals: they share the same structural parameters at fixed mass and the same scaling relations. On the other hand, the population of field ellipticals at z~1.3 shows a significant lack of massive (M*> 2×10^{11} Msun) and large (Re > 4-5 kpc) ellipticals with respect to the cluster. Nonetheless, at M*< 2×10^{11} Msun, the two populations are similar. The size-mass relation of cluster and field ellipticals at z~1.3 defines two different regimes, above and below a transition mass m_t~2-3×10^{10} Msun: at lower masses the relation is nearly flat (Re\propto M*^{-0.1\pm0.2}), the mean radius is constant at ~1 kpc and, consequenly, Sigma_Re ~ Sigma_1kpc while, at larger masses, the relation is Re\propto M*^{0.64\pm0.09}. The transition mass marks the mass at which galaxies reach the maximum Sigma_Re. Also the Sigma_1kpc-mass relation follows two different regimes, above and below m_t, (Sigma_1kpc\propto M*^{0.64\ >m_t}_{1.07\ <m_t}) defining a transition mass density Sigma_1kpc~2-3×10^3 Msun pc^{-2}. The effective stellar mass density Sigma_Re 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, Sigma_1kpc, besides to be 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. [Abridged]

Read this paper on arXiv…

P. Saracco, A. Gargiulo, F. Ciocca, et. al.
Fri, 23 Sep 16

Comments: Accepted for publication in A&A; 20 pages, 13 figures