Extragalactic large-scale structures behind the Southern Milky Way^*

II. Redshifts obtained at the SAAO in the Crux region

¹ Department of Astronomy, University of Cape Town, Rondebosch, 7700, South Africa
² Observatoire de Paris, DAEC, Unité associée au CNRS, D0173, et à l'Université Paris 7, 92195 Meudon Cedex, France

Send offprint request to: A.P. Fairall

Received: 20 January 1997
Accepted: 20 May 1997

Abstract

In our systematic optical galaxy search behind the southern Milky Way, 3760 (mostly unknown) galaxies with diameters were identified in the Crux region (, Woudt & Kraan-Korteweg 1997). Prior to this investigation, only 65 of these galaxies had known redshifts. In order to map the galaxy distribution in redshift space we obtained spectra for 226 bright () objects with the 1.9 m telescope of the South African Astronomical Observatory (SAAO). 
Redshifts could be determined for 209 objects, of which 173 have good signal-to-noise ratios. Of the 36 tentative redshifts, four are confirmed through independent values in the literature. The redshifts of three objects indicate them to be galactic in origin. One of these confirms a suspected Planetary Nebula. For 17 of the galaxies, no redshift could be determined due to poor signal-to-noise ratios. 
In addition, 26 redshifts have have been measured in the Hydra-Antlia region investigated earlier (Kraan-Korteweg et al. 1995), of which one is a tentative estimate.
Two main structures crossing the Galactic Plane in the Crux region have now become clear. A narrow, nearby filament from ( to the Centaurus cluster can be traced. This filament runs almost parallel to the extension of the Hydra–Antlia clusters found earlier and is part of what we have earlier termed the "Centaurus Wall” extending in redshift-space between 6000  km s^-1 (Fairall & Paverd 1995). The main outcome of this survey however, is the recognition of another massive extended structure between  km s^-1 . This broad structure, dubbed the Norma Supercluster (Woudt et al. 1997), runs nearly parallel to the Galactic Plane from Vela to ACO 3627 (its centre) from where it continues to the Pavo cluster. This massive structure is believed to be associated with the Great Attractor.
The survey has furthermore revealed a set of cellular structures, similar to those seen in redshift space at higher galactic latitudes, but never before seen so clearly behind the Milky Way.