Stellar mass surface density versus effective radius and stellar mass. Upper panel − the effective stellar mass density within the effective radius , is plotted as a function of the effective radius R_e (left) and of the stellar mass ℳ_∗ (right). Blue filled squares are field ellipticals in the GOODS-S regions, green crosses are those in the COSMOS area, and red filled circles are cluster ellipticals. The black solid line is the best-fitting relation (see Appendix A for the orthogonal fit). The green dashed line in the right panel shows the stellar mass density as a function of mass for a constant value of R_e = 1.3 kpc (marked on the left panel), corresponding to the limiting value ~0.17 arcsec adopted for the effective radius in the COSMOS catalog of Scarlata et al. (2007). The gray dot-dashed line marks the Zone of Exclusion (ZOE) as defined in Sect. 6.1. The open stars are the early-type galaxies selected by Raichoor et al. (2011; R11) in groups and clusters at z ~ 1.27. The open triangles are the cluster elliptical galaxies at 1.22 <z< 1.4 studied by Delaye et al. (2014; D14).The cyan crosses are the elliptical galaxies from CANDELS. Lower panel − the central stellar mass density calculated within 1 kpc radius (Σ_{1 kpc}) is plotted as a function of the effective radius (left) and of the stellar mass (right). Symbols are as in the upper panel. The solid black line is the best-fitting broken power law for ℳ_∗>m_t and for ℳ_∗<m_t, with m_t = 2.5 × 10¹⁰M_⊙. The gray dashed line is the relation found by Tacchella et al. (2016) with their model of mass growth and quenching, arbitrarily normalized.Errorbars are not shown to observe the agreement among the different samples and the relations defined by the data.