| 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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