FORS spectroscopy of galaxies in the Hubble Deep Field-South

¹ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK e-mail: dar@astro.ox.ac.uk
² Max-Planck-Institut für extraterrestrische Physik (MPE), Postfach 1312, Garching 85741, Germany
³ USRA, NASA Ames Research Center, MS 144-2 Moffett Field, CA 94035-1000, USA
⁴ Dipartimento di Astronomia, Universita' di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
⁵ Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA

Received: 24 July 2003
Accepted: 18 December 2004

Abstract

We present low resolution multi-object spectroscopy of an I-band magnitude limited ( 23–23.5) sample of galaxies located in an area centered on the Hubble Deep Field-South (HDFS). The observations were obtained using the Focal Reducerlow dispersion Spectrograph (FORS) on the ESO Very Large Telescope. Thirty-two primary spectroscopic targets in the HST-WFPC2 HDFS were supplemented with galaxies detected in the Infrared Space Observatory's survey of the HDFS and the ESO Imaging Deep Survey to comprise a sample of 100 galaxies for spectroscopic observations. Based on detections of several emission lines, such as [OII]λ3727, H and [OIII]λ5007, or of other spectroscopic features, we measured accurate redshifts for 50 objects in the central HDFS and flanking fields. The redshift range of the current sample of galaxies is 0.6–1.2, with a median redshift of 1.13 (at I  23.5 not corrected for completeness). The sample is dominated by starburst galaxies with only a small fraction of ellipticals (~10%). For the emission line objects, the extinction corrected [OII]λ3727 line strengths yield estimates of star formation rates in the range 0.5–30  yr^-1. We used the present data to derive the [OII]λ3727 luminosity function up to redshift of 1.2. When combined with [OII]λ3727 luminosity densities for the local and high redshift Universe, our results confirm the steep rise in the star formation rate (SFR) to z  1.3.