The density of very massive evolved galaxies to z similar or equal to 1.7

We spectroscopically identified seven massive, evolved galaxies with magnitudes 17.8 < K < 18.4 at 1.3 < z < 1.7 over an area of ∼160 arcmin² of the MUNICS survey. Their rest-frame K-band absolute magnitudes are −26.8 < M_K < −26.1 (5L* < L_K < 10L*) and the resulting stellar masses are in the range 3–6.5 × 10¹¹ M_⊙. The analysis we performed unambiguously shows the early-type nature of their spectra. The seven massive, evolved galaxies account for a comoving density of (5.5 ± 2) × 10⁻⁵ Mpc⁻³ at 〈z〉≃ 1.5, a factor 1.5 lower than the density [(8.4 ± 1) × 10⁻⁵ Mpc⁻³] of early types with comparable masses at z= 0. The incompleteness (∼30 per cent) of our spectroscopic observations accounts for this discrepancy. Thus, our data do not support a decrease of the comoving density of early-type galaxies with masses comparable to the most massive ones in the local Universe up to z≃ 1.7. This suggests that massive evolved galaxies do not play an important role in the evolution of the mass density outlined by recent surveys in this redshift range, evolution which instead has to be ascribed to the accretion of the stellar mass in late-type galaxies. Finally, the presence of such massive evolved galaxies at these redshifts suggests that the assembly of massive spheroids has taken place at z > 2 supporting a high efficiency in the accretion of the stellar mass in massive haloes in the early Universe.