We present the results of TNG near-IR low resolution spectroscopy of two (S7F5254 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 S7F5254 and z =~ 1.46+/-0.02 for S7F545. The resulting lower limits to their stellar mass are Mstarsmin=6*E11 Msun and Mstarsmin=4*E11 Msun. The minimum age of the last burst of star formation in S7F5254 is 3.5 Gyr while it is 0.5 Gyr in S7F545 implying a minimum formation redshift zf>≈3 .5 and zf>≈2 for the two EROs respectively.
Massive z ~ 1.3 evolved galaxies revealed
2003
Abstract
We present the results of TNG near-IR low resolution spectroscopy of two (S7F5254 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 1.2I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
