| The 21-cm spectral line of hydrogen (HI)
traces the cold atomic hydrogen gas in galaxies, which typically extends well
beyond their stellar disks. The HI velocity fields shown in the image above
are for two nearby dwarf galaxies, ESO223-G009 (left) and ESO215-G?009 (right),
observed as part of the
Local Volume HI Survey (LVHIS). The near circular HI gas
distributions of galaxies suggest nearly face-on orientations, but the two
velocity fields tell a different story. Both galaxies are warped, ie. their
disk inclination and position angles vary with radius. The origin of warps
is still a topic of investigation.
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