By Chris Conselice

ESO510-G13 taken with the Very Large Telescope (VLT) Image Copyright: ESO

Galaxies come in all shapes and sizes. Perhaps the most remarkable difference between galaxies is the huge variation in their appearance. Galaxies that look like ESO 510-G13 are very rare in the nearby universe. ESO 510-G13 contains a large spheroidal bulge surrounded by a severely warped disk. Galaxies with disks and bulges are not unusual in the universe, nor are the warps seen in ESO 510-G13. What makes ESO 510-G13 unique is that it's disk has an obvious strong warp that is the result of a galaxy interaction.

In the nearby universe galaxy interactions are spectacular, but rare. Less than 5% of galaxies are currently undergoing a strong interaction with another galaxy of similar mass. In the distant universe we see many more galaxies undergoing interactions, with perhaps as many as half involved in what are called major mergers where two galaxies merge together to form a new galaxy. It is now thought that most galaxies we see today originated from this merging process.

Digitized Sky Survey (DSS) image of ESO 510-G13 Image Credit: DSS

ESO 510-G13 is unique in that several scenarios could be responsible for producing it's structure. The warped disk could result from a fly-by encounter of a galaxy, or, a more interesting possibility, the warped disk itself is the remains of a galaxy captured by ESO 510-G13 in the past.

Small disk warps around galaxies are not uncommon however, and most galaxies show some form of a warp when viewed in the distribution of their internal hydrogen gas. Stellar warps, like the one seen in ESO 510-G13, are not as common, but small stellar warps are seen in several other galaxies. Our nearest large neighbor, the spiral galaxy M31, also has a warped stellar disk, probably the result of an interaction with the Milky Way.

The different colors in the image of ESO 510-G13 demonstrate the variety of physical effects occurring. The white-colored central bulge is dominated by older stars, many of which have existed for at least ten billion years. The warped disk contains young blue stars that were recently formed less than a couple hundred-million years ago. This star formation is probably triggered by the interaction that produced the warp itself. Several dark dust lanes can also be seen trisecting the image. Dark dust lines like these are commonly seen in edge-on disk galaxies and are also often associated with star formation.