The Fornax spectroscopic survey I. Survey strategy and preliminary resultson the redshift distribution of a complete sample of stars and galaxies

The Fornax Spectroscopic Survey will use the Two degree Field spectrograph (2dF) of the Angle-Australian Telescope to obtain spectra for a complete sa mple of all 14000 objects with 16.5 less than or equal to b(j) less than or equal to 19.7 in a 12 square degree area centred on the Fornax Cluster. Th e aims of this project include the study of dwarf galaxies in the cluster ( both known low surface brightness objects and putative normal surface brigh tness dwarfs) and a comparison sample of background field galaxies. We will also measure quasars and other active galaxies, any previously unrecognise d compact galaxies and a large sample of Galactic stars. By selecting all o bjects-both stars and galaxies-independent of morphology, we cover a much l arger range of surface brightness and scale size than previous surveys. In this paper we first describe the design of the survey. Our targets are s elected from UK Schmidt Telescope sky survey plates digitised by the Automa ted Plate Measuring (APM) facility. We then describe the photometric and as trometric calibration of these data and show that the APM astrometry is acc urate enough for use with the 2dF. We also describe a general approach to o bject identification using cross-correlations which allows us to identify a nd classify both stellar and galaxy spectra. We present results from the first 2dF field. Redshift distributions and vel ocity structures are shown for all observed objects in the direction of For nax, including Galactic stars? galaxies in and around the Fornax Cluster, a nd for the background galaxy population. The velocity data for the stars sh ow the contributions from the different Galactic components, plus a small t ail to high velocities. We find no galaxies in the foreground to the cluste r in our 2dF field. The Fornax Cluster is clearly defined kinematically. Th e mean velocity from the 26 cluster members having reliable redshifts is 15 60 +/- 80 km s(-1). They show a velocity dispersion of 380 +/- 50 km s(-1). Large-scale structure can be traced behind the cluster to a redshift beyon d z = 0.3. Background compact galaxies and low surface brightness galaxies are found to follow the general galaxy distribution.