The histogram of redshifts shown in Fig. 4 (click here) reveals a broad
concentration of galaxies around 
8500 km s-1, with a probable
dip at 4500 km s-1. This is quite different to the single peak
centred at 2750 km s-1 for the neighbouring Hydra-Antlia region
to the west (Paper I), and the dominating peak at 4882 km s-1 of
the Norma cluster (KK96) to the east. It suggests that quite
different large-scale structures may be present in this Crux region,
which we shall examine in greater detail below.
Figure 4: Velocity histogram of the galaxies in the search area
in the Crux extension in the ZOA. Lighter hatched areas are velocities
measured by us; darker hatched are previous observations by others
In regard to the interpretation of data in three-dimensional redshift space, particularly in the absence of magnitude controls, the reader is directed to the introductory discussion in Sect. 3.2 (click here) of Paper I. In interpreting these plots, note that the Hydra-Antlia ZOA region is covered observationally as deep as the current Crux region, whereas other low-latitude regions only have very sparse redshift information
Figure 5: Sky projections in galactic coordinates for redshift intervals
of 
. Within the panels the redshifts
are subdivided into intervals of 
:
filled squares mark the nearer redshift interval (e.g., 
km s-1 in
the top-left panel), crosses the more distant interval (
km s-1 in same panel). The skyplots increase in velocity-distance from the
top-left panel to the bottom-right panel as marked above each panel.
The area of our investigation is outlined
Figure 5 (click here) shows the surveyed region and its surrounding volume sliced
in redshift intervals of . As already
indicated, most of the data points, within the outlined Crux region, are
from the new observations. Conspicuous features occur in the second and
third slices - matching the excess already noted in the histogram of
Fig. 4 (click here).
In the second slice, the new data reinforce the presence of a narrow filamentary
structure running all the way from 
, 
to the Centaurus cluster at 
, 
.
This is believed to be part of a Great Wall-like structure seen edge-on
- the Centaurus Wall.
The new observations fill in a portion of
this feature previously hidden by the Milky Way - as might be expected of a
continuous massive structure.
The break, due to the obscuration close to the galactic plane
is now much narrower. The new data in the top-left corner of the Crux
region is concentrated in the 3500-4500 km s-1
range - slightly closer than most other condensations within the wall.
There are also indications of weaker filaments: One crosses north-south
at 
while another passes just outside the south-east corner
of the surveyed area.
However, the most important structure revealed by the present survey
occurs in the third slice down. This is a concentration of galaxies
centred at 5000 km s-1 in the upper (northern) segment of the surveyed
volume. Together with the neighbouring galaxies outside the survey
volume, it suggests a large-scale structure running more or less
horizontally across the diagram. We have earlier labelled this structure
as the "Norma supercluster'' (Woudt et al. 1997). Traces can
also be seen in the following slice, so the feature is also probably
wall-like seen roughly side on - i.e. its width (or depth in Fig. 5 (click here))
being some 3000 km s-1 and its thickness several hundred km s-1 unless much
is still hidden by the dense obscuration. We shall see however (in
Fig. 6 (click here)) that this feature is more complex. For the moment note the
concentration at in the fourth slice - coincident with that
seen earlier in Fig. 1 (click here). Bearing in mind its greater distance,
compared to the Centaurus Wall mentioned above, this new structure must be
similarly massive.
The Norma cluster is situated where these two massive structures - the
Centaurus Wall and the Norma supercluster - intersect.
Features at greater redshifts are understandably narrower in angular dimensions, and more difficult to discern: The fourth slice shows a feature running along the southern boundary of the Crux region. Beyond that, the data is generally too sparse, except for a weak concentration at 14000 - 16000 km s-1 in the south-east (bottom left), that corresponds to the relatively distant overdensity noted earlier.
Figure 6: Redshift slices out to v < 10000 km s-1
for the longitude range 
. The top panels display the structures above
the GP (
) the middle panel in the GP
(
) and the bottom panel the structures below
the GP (
). The dashed lines in the middle panel
delimits the survey area. Filled squares are measurements from
the SAAO, crosses from the literature
Our final set of plots, Fig. 6 (click here), shows slices in galactic latitude; the uppermost including the Centaurus and Hydra clusters, the lowest the Pavo cluster.
The product of our survey appears as the middle slice, which would otherwise be largely blank. Instead, the slice reveals a cellular structure - familiar from plots elsewhere in the sky (e.g. Fairall et al. 1990) - but never before discerned so clearly at so low a galactic latitude. Presumably, the appearance is somewhat assisted by a favourable angle of cut. The cell sizes, and the voids so contained, are 1000-2000 km s-1 in diameter.
Of particular interest is a radial feature (from 5300 to 7000 km s-1),
almost dead centre, that corresponds to the
concentration at galactic longitude . The feature
could be the "finger of God'' of a small cluster except it is not
discernable as such in a central longitude slice (not reproduced here).