5 Summary

A deep optical galaxy search for obscured galaxies behind the dust layer and crowded star fields of the Milky Way revealed 3279 galaxy candidates of which only 112 (3.4%) were previously catalogued and of which 127 (of the 227 positional matches) have a reliable counterpart in the IRAS PSC.

A comparison with the foreground extinction levels (Schlegel et al. 1998) indicates that galaxies remain easily detectable through obscuration layers of 3 magnitudes of extinction and recognisable up to levels of ${A}_{ B} = 5\hbox{$.\!\!^{\rm m}$ }0$. At higher extinction levels, the Milky Way remains mostly opaque. Overall, the mean number density follows the dust distribution remarkably well.

An analysis of the completeness of this visual search indicates that we are complete to a diameter limit of ${D} = 14\hbox{$^{\prime\prime}$ }$. Correcting the observed parameters for the foreground obscuration (DIRBE extinction values with Cameron extinction corrections) we find that our ZOA survey is complete to ${ D}^{\rm o} \ge 60\hbox{$^{\prime\prime}$ }$ and - depending on the surface brightness of the galaxy - to for foreground obscuration levels of ${ A_B} \le 3\hbox{$.\!\!^{\rm m}$ }0$. 277 galaxies were identified above this diameter limit compared to the 76 in this area by Lauberts. These numbers demonstrate the success of deep visual galaxy searches at low Galactic latitudes.

With the understanding of our completeness limit for extinction-corrected galaxies, the first step in arriving at a complete whole-sky survey with a considerably reduced ZOA could be undertaken (cf., Fig. 7, i.e. a southern-sky galaxy distribution complete to ${ D}^{\rm o} \ge 1\hbox{$.\mkern-4mu^\prime$ }3$ for extinction levels of ${ A_B} \le 3\hbox{$.\!\!^{\rm m}$ }0$).

Several distinct overdensities and filaments of galaxies can be identified that are apparently uncorrelated with the Galactic foreground extinction hence the probable signature of extragalactic large-scale structures. The catalog (the first in a series of five) build the basis for various spectroscopic and photometric follow-up programs.

Acknowledgements

Foremost, I would like to thank P.A. Woudt for many stimulating discussions. Without the prestation of the old blinking machine from the Astronomical Institute of Basel and the donation of the surveyed film copies of the ESO/SRC survey by ESO, this project could not have been pursued. The derivations of positions, diameters and magnitudes for the visually detected galaxies on F213 from COSMOS scans by H. MacGillivray were extremely valuable for the analysis. The enthousiastic collaborations with my colleagues C. Balkowski, V. Cayatte, A.P. Fairall, P.A. Henning and P.A. Woudt in the various redshift follow-ups programs is greatly appreciated.