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Dwingeloo 1 & 2 revisited (again)

Submitter: Tom Oosterloo & Gyula Jozsa
Description: In recent months, we have seen the Dwingeloo dish starting a 2nd life. So it is important to re-iterate that in its first life, the telescope has made many important contributions to astronomy. One of these is the discovery of two nearby galaxies: Dwingeloo 1 and Dwingeloo 2. These galaxies have had some attention in the Daily Images (see http://www.astron.nl/dailyimage/main.php?date=20071011). The galaxies were discovered with the Dwingeloo dish in 1994 and shortly after re-observed, in much more detail, with the WSRT. However, these data are not available anymore in digital form. This is unfortunate because there are no nice good quality illustrations available of the radio images of Dwingeloo 1 & 2. This weekend, a small hole in the WSRT schedule was used to observe the neutral hydrogen in "our" galaxies, resulting in the image shown here.

Dwingeloo 1 & 2 were discovered about 15 years ago in DOGS: the Dwingeloo Obscured Galaxy Survey. This discovery was published in a Nature paper (Kraan-Korteweg et al., Nature 372, p77). This survey used the Dwingeloo dish to look for galaxies that are behind the plane of our Galaxy (the band of diffuse light that one can see in the sky on dark nights). Dust clouds in the Galactic Plane absorb the optical light of galaxies that are behind the plane and such galaxies are therefore very hard to see. On the other hand, the Galactic Plane is transparent for the radiation of neutral hydrogen. Therefore, surveying the Galactic Plane with instruments like the Dwingeloo dish can reveal galaxies that are otherwise hard to see. And indeed, DOGS found these 2 galaxies. Quite interestingly, they are very close to us, they are member of the Maffei group of galaxies, at a distance of only 10 million lightyears.
Copyright: Astron
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