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Appendix A: Stellar masses, age and absolute magnitudes for different models

The table reports the age [Gyr], the stellar mass [log (M/M_⊙)], and the absolute magnitudes for each galaxy of the sample in the B and R bands derived by best-fitting their spectral energy distribution with the stellar population synthesis models of Maraston (2005, MA05), Bruzual & Charlot (2003; BC03), and the later release by Charlot & Bruzual (2007; CB07). The last row reports the mean values. We considered two different initial mass functions (IMFs): the Salpeter IMF for the MA05 and BC03 models and the Chabrier IMF for the BC03 and CB07 models. As expected, the absolute magnitudes depend neither on the model nor on the IMF adopted since the color k-correction term can vary with different models of hundredth of a magnitude. It can be seen that also the mean age of the stellar population is very stable with respect to the model used and to the IMF adopted. In contrast, the IMF, as is known, systematically affects the stellar mass with the Salpeter IMF producing masses about 1.7 times higher than the Chabrier IMF.

Appendix B: Surface-brightness profile fitting

The structural parameters of the galaxies were derived by fitting the observed surface brightness profile in the F850LP-band image with a Sérsic profile convoluted with the PSF using Galfit, as described in Sect. 3.2. In this appendix the 16 ellipticals of the sample selected according to the criteria described in Sect. 2.2 are shown (upper panels), together with the best-fitting surface brightness model (middle panels) and the residuals (lower panels). The images are 3 × 3 arcsec. The convolution box and the fitting box (6 × 6 arcsec) were defined by repeatedly fitting the observed profile with increasing values of the box until the convergence of the best-fitting parameter values. The goodness of the fit is shown by the lack of residuals obtained for all the galaxies. It is also worth noting that no structures are visible in the residuals, showing the regularity and the symmetry of the true profile. The good fitting is also shown in Fig. B.2 where the observed surface brightness profile measured on the F850LP image is compared with the best fitting model profile. In all cases, the profile of the galaxies were fit over at least five magnitudes in surface brightness. The observed surface brightness profiles of galaxies #5, #626, and #657 depart from the model profiles at r ~ 0.5 arcsec, the mean distance between them.

Fig. B.1 Each column shows the GALFIT input and output for the 16 cluster ellipticals at z = 1.27: ACS − F850LP band image of the galaxy (upper box), best-fitting Sérsic model profile (middle box) and residual image (lower box) obtained by subtracting the model from the image. Galaxies are (from top left to bottom right): (upper panel) ID. #1, #2, #3, #4, #5 #626 and #657, #606, #590; (lower panel) #568, #719, #1250, #173, #1160, #1471. Each image is 3 × 3 arcsec.

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Fig. B.2 Surface brightness in the F850LP band measured within circular annulus centered on each galaxy (black points), compared with the surface brightness resulting from the best fitting Sérsic model profile (red points). The dotted line marks the radius of the FWHM while the dot-dashed line marks the effective radius. In the lower panels the residuals of the fitting obtained as the difference between the data points and the models are shown.

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© ESO, 2014