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A&A Supplement series, Vol. 127, February I 1998, 463-470

Received January 20; accepted May 20, 1997

Extragalactic large-scale structures behind the Southern Milky Way

II. Redshifts obtained at the SAAO in the Crux regiongif

A.P. Fairalltex2html_wrap1278 - P.A. Woudttex2html_wrap1278 - R.C. Kraan-Kortewegtex2html_wrap1282

Send offprint request: A.P. Fairall

tex2html_wrap1284  Department of Astronomy, University of Cape Town, Rondebosch, 7700, South Africa
tex2html_wrap1286  Observatoire de Paris, DAEC, Unité associée au CNRS, D0173, et à l'Université Paris 7, 92195 Meudon Cedex, France


In our systematic optical galaxy search behind the southern Milky Way, 3760 (mostly unknown) galaxies with diameters tex2html_wrap_inline1258 were identified in the Crux region (tex2html_wrap_inline1260, 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 (tex2html_wrap_inline1262) 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 (tex2html_wrap_inline1264 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 tex2html_wrap_inline1266 6000 km s-1 (Fairall & Paverd 1995). The main outcome of this survey however, is the recognition of another massive extended structure between tex2html_wrap_inline1270 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.

keywords: galaxies: redshifts -- galaxies: clusters of -- large-scale structure of the Universe

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