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8th of May 2015
Untangling an extremely warped dwarf galaxy
by Peter Kamphuis (CASS)
Warps in neutral hydrogen (HI) disks are common in spiral galaxies. So common that it is thought that whenever an HI disk extends beyond the optical disk it is warped. Their exact origin is still a matter of debate. In order to better understand the origin of warps it is crucial to be able to map this bending of the gas disk accurately. To do this in many hundreds of galaxies we have developed a code that can fit all kinds of warps in HI disks, the Fully Automated Tilted Ring Fitting Code (FAT, Kamphuis et al. 2015, submitted). The image above shows an example of the strength of this fitting code. On the left it shows the velocity field of the extremely warped, dwarf galaxy ESO223-G009, which also featured yesterday on ADAP and was observed as part of the Local Volume HI Survey (LVHIS). On the right it shows the velocity field of the model that was fitted by FAT; it is easy to see that they agree well. Additionally, we learn that in this galaxy the position angle of the disk changes by almost 150 degrees as we move out in radius. With FAT we can now apply this fitting technique to a large sample and thus investigate the origin of warps.

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