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The Parkes HI Zone of Avoidance Survey

Submitter: George Heald
Description: A blind HI survey of the extragalactic sky behind the southern Milky Way has been conducted with the multibeam receiver on the 64-m Parkes radio telescope. The survey covers the Galactic longitude range 212 degr < l < 36 degr and Galactic latitudes |b| < 5 degr. This region is historically called the "Zone of Avoidance" because distant galaxies seemed to avoid the region — we now know that they are present there, but are obscured and confused by our own Galaxy in the foreground. The new survey provides an rms sensitivity of 6 mJy per beam per 27 km/s channel, and yields 883 galaxies to a recessional velocity of 12,000 km/s. One third of the detected galaxies had not been previously recognized. The survey covers the sky within the HI Parkes All-Sky Survey (HIPASS) area to greater sensitivity, finding lower HI-mass galaxies at all distances, and probing more completely the large-scale structures at and beyond the distance of the Great Attractor. Several newly identified mass concentrations have been uncovered with this new dataset.

The image above shows the HI detections overlaid on the dust map in this region of sky (top) and on the continuum map (bottom), proving that the Parkes HI Zone of Avoidance Survey (HIZOA) is not affected by dust and only little by continuum emission in the foreground.

A paper describing all of this work has been published today in the Astronomical Journal. The author list includes experts in the study of the Zone of Avoidance, some of whom used the Dwingeloo 25-m telescope for a similar, complementary survey in the 90s. In future, the SKA and its pathfinders will explore this region and the rest of the extragalactic HI sky to even greater detail.
Copyright: Staveley-Smith, Kraan-Korteweg, Schröder, Henning, Koribalski, Stewart and Heald
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