News & Results

An interesting source found in the HI Zone of Avoidance Survey.

This source is hiding behind our Galaxy at a distance of ~18 Mpc, located at a galactic latitide of 0 degrees. To the right is a neutral hydrogen (HI) image of the source and its surroundings from the Parkes Multibeam instrument . It is well obscured by Galactic gas, dust and high stellar densities in most optical wavelengths. Please note the scales on the side of the images, the Galactic Equator is marked as 0 degrees. (Click on the images for full size)

This B&W image is from the UKST Digital Sky Survey, in the R-Band, and is centered on the position of the HI detection. The image is 6 X 6 arcmin which only covers the central portion of the source. As we can see, nothing but stars may be seen down to the fainest sources.

As we look towards longer wavelengths, 60 micron, to try and penetrate the Galactic Plane, we still see confusion from galactic sources. This is an image from the IRAS Galaxy Catalog super resolved to 1-2 arcminute resolution. The overlayed contours are HI Total Power from the multibeam. As we can see there is a lot of sources within the contours of the HI source, however, none seem to be an easily identifiable candidate.

Since we can not see in the optical wavelengths, lets have a look at longer centimeter wavelengths which pentrate the Galactic Plane gas and dust. This is a MOST image at a wavelength of 35cm. If the image seems some what confusing that is because the MOST is a continuum radio telescope and when it looks in the direction of our Galaxy it detects radiation from sources within our Galaxy and from sources that may lie behind our Galaxy. So we are faced with another problem of being confusion limited at the galactic equator. The very white blobs and wisps are HII regions and supernova remnents respectively. At this wavelength we would expect the identification to look more like one of the more fainter point sources.

Being a difficult source to see, we've observed it with the Australia Telescope Compact Array (ATCA). With higher resolution and sensitivity, we've imaged the central portion of the source at 21cm. We found that the source resolved into several complex features with in a faint envelope of neutral hydrogen. Suggesting that we may not be looking at one source but several, perhaps at the stage of merging. Because galactic HI envelopes are so huge compared to the optical picture of a galaxy, quite often we may find systems that are interacting by looking at their HI structure.

We found this source to be very mysterious. We next had a look at the velocity field of the ATCA observations of this source, left. We found galaxy type rotation (blue rotating towards us and red rotating away from us) with some unusual wisps towards the north of the source. Indeed could we be looking at an interacting system, the merger of two galaxies with the fainter wisps being gravitationaly collapsing neutral hydrogen regions. We hope that current analysis will determine what this system is.

This page is maintained by Sebastian Juraszek
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