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 M_K ~ -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 for S7F5-254 and z=1.46 for S7F5-45. The resulting lower limits to their stellar mass are M_{stars}=6x10^{11} M_{sun} and M_{stars}=4x10^{11} M_{sun}. 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 z_f>3.5 and z_f>2 for the two EROs respectively.
@article{arxiv.astro-ph/0211394,
title = {Massive z ~ 1.3 evolved galaxies revealed},
author = {P. Saracco and M. Longhetti and P. Severgnini and R. Della Ceca and F. Mannucci and R. Bender and N. Drory and G. Feulner and F. Ghinassi and U. Hopp and C. Maraston},
journal= {arXiv preprint arXiv:astro-ph/0211394},
year = {2009}
}
Comments
Accepted for publication on A&A; 7 pages, 5 figures