FORS spectroscopy of galaxies in the Hubble Deep Field-South

We present low resolution multi-object spectroscopy of an I-band magnitude limited (I-AB similar or equal to 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 Reducer/low 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]lambda 3727, H-beta and [OIII]lambda 5007, 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 similar or equal to 23.5 not corrected for completeness). The sample is dominated by starburst galaxies with only a small fraction of ellipticals (similar to 10%). For the emission line objects, the extinction corrected [OII]lambda 3727 line strengths yield estimates of star formation rates in the range 0.5-30 M circle dot yr(-1). We used the present data to derive the [OII]lambda 3727 luminosity function up to redshift of 1.2. When combined with [OII]lambda 3727 luminosity densities for the local and high redshift Universe, our results confirm the steep rise in the star formation rate (SFR) to z similar or equal to 1.3.