A VLT/FORS2 spectroscopic survey in the HDF-S^*

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
² Dipartimento di Astronomia dell'Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
³ INAF – Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 40131 Trieste, Italy
⁴ Space Telescope European Coordinating Facility, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁵ Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
⁶ INAF – Osservatorio Astronomico di Roma, via dell'Osservatorio 2, Monteporzio, Italy
⁷ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, Merate, Italy

Corresponding author: E. Vanzella, evanzell@eso.org

Received: 21 June 2002
Accepted: 30 September 2002

Abstract

We report on low-resolution multi-object spectroscopy of 65 objects from to in the HDF-S obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS2). 18 objects belong to the HDF-S proper, i.e. the WFPC2 deep area. 15 high-redshift galaxies with (10 in the HDF-S proper) have been identified. The spectroscopic redshifts are in good agreement with the photometric ones derived from a minimization technique comparing the observed spectral energy distribution with synthetic libraries and with a new neural network (NN) approach. The dispersion with the former method is whereas the latter provides . No “catastrophic” difference is encountered. The inferred star formation rates of the individual objects range from tens to a few hundreds of yr^-1 and the global star formation rate of the Universe at is estimated to be 0.15 yr^-1 Mpc^-3 with a statistical error of 0.04. 
Evidence for large-scale structure is found with two groups' redshifts observed at and and a pronounced low redshift peak around .
An elliptical galaxy lensing a background object turns out to be at a redshift .