We present the results of TNG near-IR low resolution spectroscopy of two (S7F5_254 and S7F5_45) sources belonging to a complete sample of 15 EROs with K < 18 and R − K > 5 selected from the MUNICS Survey. Both the spectra show a sharp drop in the continuum which can be ascribed only to the Balmer break. This places them at 1.2 < z < 1.5. Their rest-frame z = 1.2 K-band absolute magnitude is MK ≃−26.6 (L ∼ 7L∗). The comparison of the spectra and the photometric data with a grid of synthetic template spectra provides a redshift z 1.22−0.07 +0.2 for S7F5_254 and z ≃ 1.46 ± 0.02 for S7F5_45. The resulting lower limits to their stellar mass are Mmin stars = 6 × 1011 M⊙ and Mmin rstars = 4 × 1011 M⊙. The minimum age of the last burst of star formation in S7F5_254 is 3.5 Gyr while it is 0.5 Gyr in S7F5_45 implying a minimum formation redshift zf ≳ 3.5 and zf ≳ 2 for the two EROs respectively.
- galaxies : evolution
- galaxies : elliptical and lenticular, cD
- galaxies : formation