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23-09-2010
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Witnessing the formation of a warp

Submitter: Gyula I.G. Jozsa
Description: NGC 660 is a famous example of a strongly warped spiral galaxy: with increasing radius, its disk bends more and more away from its inner orientation, until it reaches a tilt of more than 45 degrees. While this is an extreme case, warping is not unusual for disk galaxies, however, they are usually not so obvious. But by observing the gaseous disk at a radius beyond the stars with a radio telescope, one will probably find a warped disk in most spiral galaxies.
Since the phenomenon is so common, many theories for warp formation have been developed. Some connect warps with interactions between galaxies. Recent observations of the neutral hydrogen (red in the image) with the Westerbork Synthesis Radio Telescope (WSRT) show that such an interaction might well have caused the warping of the disk of NGC 660. The image shows a gaseous stream stretching all the way from NGC 660 to its neighbor UGC 1195, over more than 290,000 light years. This suggests that both galaxies did probably have an encounter in their past, which might have resulted in the warp of NGC 660.
Some theories explain the formation of warps and polar ring by the capture of gas from a companion galaxy during such an encounter, which then forms an outer, misaligned disk evolving into a ring or a warp. We see that a lot of gas is exchanged between UGC 1195 and NGC 660. Are we thus witnessing warp formation through gas-capture?
Copyright: ASTRON
 
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