Mapping the Hidden Universe:
The Galaxy Distribution in the Zone of Avoidance

Ren\'ee C. Kraan-Korteweg , Sebastian Juraszek, PASA, 17 (1), 6.

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Deep Optical Galaxy Searches

Systematic deeper searches for ``partially obscured'' galaxies - down to fainter magnitudes and smaller dimensions (

${\rm D} \,\raisebox{-0.4ex}{$\stackrel{>}{\scriptstyle\sim}$}\,0\hbox{$.\mkern-4mu^\prime$}1$) than existing catalogs - have been performed with the aim to reduce this ZOA. Using existing sky surveys (POSS I and POSS II in the north and the ESO/SERC surveys in the south), the whole ZOA has in the mean time been visually surveyed for galaxies. Here, examination by eye is still the best technique. A separation of galaxy and star images can as yet not be done by automated measuring machines (e.g. COSMOS or APM) on a viable basis below

$\vert b\vert \,\raisebox{-0.4ex}{$\stackrel{<}{\scriptstyle\sim}$}\,10{^\circ}-15{^\circ}$ though surveys by eye are clearly both very trying and time consuming, and maybe not as objective.

Figure: An overview of the different optical galaxy surveys in the ZOA centered on the Galaxy. The labels identifying the search areas are explained in the text. Note that the surveyed regions entirely cover the ZOA defined by the foreground extinction level of

${\rm A_B} = 1\hbox{$.\!\!^{\rm m}$}0$ in Fig. 1.

\begin{figure} \begin{center} \hfil \psfig{file=figcor.ps,width=16cm}\hfil \end{center}\end{figure}

The various surveyed regions are displayed in Fig. 2. Details and results on the uncovered galaxy distributions for the various regions are discussed in:

A: the Perseus-Pisces Supercluster by Pantoja 1997;
B1-3: the northern Milky Way (B1 by Seeberger etal. 1994, Seeberger, Saurer & Weinberger 1996, Lercher, Kerber & Weinberger 1996, Saurer, Seeberger & Weinberger 1997, and Seeberger & Saurer 1998 from POSS I; B2 by Marchiotti, Wildauer & Weinberger 1999 from POSS II; B3 by Weinberger, Gajdosik & Zanin 1999 from POSS II);
C1-3: the Puppis region by Saito etal. 1990, 1991 [C1], the Sagittarius/Galactic region by Roman, Nakanishi & Saito 1998 [C2], and the Aquila and Sagittarius region by Roman etal. 1996 [C3];
D1-5: the southern Milky Way (the Hydra to Puppis region [D1] by Salem & Kraan-Korteweg in prep., the Hydra/Antlia Supercluster region [D2] by Kraan-Korteweg 1999, the Crux region [D3] by Woudt 1998, Woudt & Kraan-Korteweg in prep., the GA region [D4] by Woudt 1998, Woudt & Kraan-Korteweg in prep, and the Scorpius region [D5] by Fairall & Kraan-Korteweg in prep.);
E: the Ophiuchus Supercluster by Wakamatsu etal. 1994, Hasegawa etal. 1999;
F: the northern GP/SGP crossing by Hau etal. 1996.

These surveys have uncovered over 50000 previously unknown galaxies and are not biased with respect to any particular morphological type. Although the various optical surveys are based on different plate material and were performed by different groups, the search techniques overall are similar. All ZOA regions have been searched to diameter limits of at least

${\rm D} \,\raisebox{-0.4ex}{$\stackrel{>}{\scriptstyle\sim}$}\,0\hbox{$.\mkern-4mu^\prime$}1$. This is considerably deeper than the previously regarded ``whole-sky'' catalogs with their completeness limits of

${\rm D} \,\raisebox{-0.4ex}{$\stackrel{>}{\scriptstyle\sim}$}\, 1\hbox{$.\mkern-4mu^\prime$}0$. How can these catalogs be merged to arrive at a well-defined whole-sky galaxy distribution with a reduced ZOA?


Next Section: Completeness of Optical Galaxy
Title/Abstract Page: Mapping the Hidden Universe:
Previous Section: Introduction
Contents Page: Volume 17, Number 1

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