Australia Telescope National Facility

DENIS Observations of Multibeam Galaxies in the Zone of Avoidance
A. Schröder , R.C. Kraan-Korteweg , G.A. Mamon, PASA, 16 (1), in press.

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Conclusions and future plans

A combination of the deep optical, systematic blind HI and NIR surveys illustrates the potential of a multi-wavelength approach for extragalactic large-scale studies behind the Milky Way. It furthermore allows the mapping of the peculiar velocity field across the ZOA through the NIR Tully-Fisher relation.

At intermediate latitudes and extinction (

$5{^\circ}\!\!<\!\!\vert b\vert\!\!<\!\!10{^\circ}$ ,

$1^{\rm m}\!\!\mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$<$}}}\!A_B\!\mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$<$}}}\!4-5^{\rm m}$ ), optical surveys remain superior for identifying galaxies due to their fainter magnitude limits. However, the NIR luminosities and colours will prove invaluable in analysing the optical survey data and their distribution in redshift space, and in the final merging of these data with existing sky surveys. Despite the high extinction and the star crowding at these latitudes, I_c, J and K_s photometry from the survey data can be successfully performed and lead, for instance, to preliminary I_c^o, J^o and K_s^o galaxy luminosity functions in A3627 (Paper II).

At low latitudes and high extinction (

$\vert b\vert < 5{^\circ}$ and

$A_B \mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$>$}}}4-5^{\rm m}$ ), the search for `invisible' obscured galaxies on existing DENIS images shows that NIR surveys can trace galaxies down to about

$\vert b\vert \simeq 1\hbox{$.\!\!^\circ$}5$ . The J-band was found to be optimal for identifying galaxies up to

$A_B \simeq 7^{\rm m}$ . NIR surveys can hence further reduce the width of the ZOA. They are furthermore the only tool that permits the mapping of early-type galaxies -- tracers of density peaks -- at high extinction.

The blind HI survey uncovers spiral galaxies independent of foreground extinction. For a significant fraction, a DENIS counterpart has been found. These MB-ZOA data covers the Galactic latitude range

$\vert b\vert <\!5{^\circ}$ . We will complement this area with pointed HI observations of optically identified spiral galaxies for intermediate latitudes (

$5{^\circ}\!< \vert b\vert <\!10{^\circ}$ ). About 300 spiral galaxies have already been detected (Kraan-Korteweg et al. 1997).

In the near future, we plan on obtaining deep K_s-band follow-up observations of the deep and complete HI-survey in the southern ZOA (cf.Juraszek, this volume). This will allow us (1) to study the effects of extinction on the extent and magnitudes of disks in the NIR, (2) to obtain a representative sample of galaxies across the ZOA for the application of the K_s-band Tully-Fisher relation, and (3) to study the morphology of the detected galaxies. The last will also be useful to understand the nature of the large-scale structures revealed with the blind HI survey, in particular as this galaxy sample can readily be merged with the southern sky HI survey (Kilbourne et al., this volume).

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Title/Abstract Page: DENIS Observations of Multibeam
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Contents Page: Volume 16, Number 1

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