Large-Scale Structures Behind the Southern Milky Way from Observations of Partially Obscured Galaxies
R.C. Kraan-Korteweg, P.A. Woudt, P.A. Henning, PASA, 14 (1), 15.
To reduce the 
-wide strip of the ZOA, we have embarked
on a deep search for partially obscured galaxies, i.e., down to fainter
magnitudes and smaller dimensions compared to existing catalogues.
To date, 50 fields of the ESO/SRC-survey have been visually
inspected. The surveyed area lies within 
- its borders are outlined
in Fig. 1.
Within the surveyed area of 
, 10276 new
galaxies with 
have been identified in addition to the
269 Lauberts galaxies with 
within
this area (Lauberts 1982). Their distributions are displayed in Fig. 1.
Figure 1: The galaxy distribution from our deep galaxy search () and the Lauberts galaxies () in
Galactic coordinates. The to date surveyed region is outlined.
The dipole direction in the CMB,
the center of the GA and the most prominent clusters are marked.
The contours mark absorption in the blue of 
= 
(thick contour), 
as derived from the Galactic
HI (Kerr et al. 1986), adopting a constant gas-to-dust ratio
and the formalism given by Burstein & Heiles 1982.
Details on the search can be found in Kraan-Korteweg & Woudt 1994.
In the mean, the galaxy density is well
correlated with the foreground extinction A
as traced
by the HI-column-density: for 
(thick contour), respectively
, the ZOA remains opaque.
Above this band, distinct filaments and round concentrations
uncorrelated with the foreground dust can be recognized, thus
they must have their origin in extragalactic
large-scale structures. Some of these features seem
to align with the known galaxy distribution, as e.g., a filament above
the Galactic Plane which points toward the Centaurus cluster,
and the filament from the Hydra and Antlia clusters towards the
prominent overdensity in Vela.
A significant overdensity, centered on the previously identified
cluster A3627 (Abell et al. 1989), is evident within only a few degrees
of the predicted center of the GA.
It is the only Abell cluster behind the Milky Way, classified as rich
and nearby and lies within the GA region. Even so, this
cluster has received little attention because of the
diminishing effects of the foreground obscuration.
And this cluster at 
) is hardly obvious in
the distribution of Lauberts galaxies and not at all in IRAS samples.
However, the galaxies in this overdensity are on average relatively large
(just below the diameter limit of Lauberts).
Lifting the obscuring veil of the Milky Way
by correcting the observed properties of the galaxies for
the foreground extinction would, in fact, reveal this cluster as the
most prominent overdensity in the southern sky.
Redshift measurements are required to map the galaxies in 3 dimensions.
The 2-dimensional galaxy distribution alone can be misleading.
For instance, the prominent overdensity in Vela was found to be due to
a superposition of a nearby (
km 
) filament connecting to
Hydra, a more distant (6000 km ) shallow extended supercluster, and
a very distant (
km ) wall-like structure crossing the ZOA
(Kraan-Korteweg et al. 1994).
© Copyright Astronomical Society of Australia 1997