Massive Z Similar To 1.3 Evolved Galaxies Revealed

Date

2003-01

Authors

Saracco, P.
Longhetti, M.
Severgnini, P.
Della Ceca, R.
Mannucci, F.
Bender, R.
Drory, N.
Feulner, G.
Ghinassi, F.
Hopp, U.

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Abstract

We present the results of TNG near-IR low resolution spectroscopy of two (S7175_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 similar or equal to -26.6 (L - 7L*). The comparison of the spectra and the photometric data with a grid of synthetic template spectra provides a redshift z similar or equal to 1.22(+0.02)(-0.07) for S7175_254 and z similar or equal to 1.46 +/- 0.02 for S7175_45. The resulting lower limits to their stellar mass are M-stars(min) = 6 x 10(11) M. and M-stars(min) = 4 x 10(11) 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 z(f) greater than or similar to 3.5 and z(f) greater than or similar to 2 for the two EROs respectively.

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Citation

Saracco, P., M. Longhetti, P. Severgnini, R. Della Ceca, F. Mannucci, R. Bender, N. Drory et al. >Massive z∼ 1.3 evolved galaxies revealed.> Astronomy and Astrophysics, Vol. 398, No. 1 (Jan., 2003) pp. 127-132