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Bully galaxy rules the neighborhood

Date:
March 21, 2010
Source:
ESA/Hubble Information Centre
Summary:
In general, galaxies can be thought of as "social" -- hanging out in groups and frequently interacting. However, a new Hubble Space Telescope image highlights how some galaxies appear to be hungry loners. These cosmic oddities have set astronomers on the "case of the missing neighbor galaxies."

This image from the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope highlights the large and bright elliptical galaxy called ESO 306-17 in the southern sky. In this image, it appears that ESO 306-17 is surrounded by other galaxies but the bright galaxies at bottom left are thought to be in the foreground, not at the same distance in the sky. In reality, ESO 306-17 lies fairly abandoned in an enormous sea of dark matter and hot gas.
Credit: NASA, ESA and Michael West (ESO)

Located half a billion light-years from Earth, ESO 306-17, is a large, bright elliptical galaxy in the southern sky of a type known as a fossil group. Astronomers use this term to emphasize the isolated nature of these galaxies. However, are they like fossils -- the last remnants of a once active community -- or is it more sinister than that? Did ESO 306-17 gobble up its next-door neighbors?

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Gravity brings galaxies together and bigger ones swallow smaller ones. There is evidence that our own Milky Way galaxy has "snacked" on numerous smaller galaxies that strayed too close. ESO 306-17 and other fossil groups may be the most extreme examples of galaxy cannibalism, ravenous systems that don't stop until they've devoured all of their neighbors.

In this image, taken by the Advanced Camera for Surveys aboard Hubble in November 2008, it appears that ESO 306-17 is surrounded by other galaxies, but the bright galaxies at bottom left are thought to be in the foreground, not at the same distance in the sky. In reality, ESO 306-17 lies fairly abandoned in an enormous sea of dark matter and hot gas.

When zooming in closely on ESO 306-17, one can see faint clusters of stars through the bright shine of the galaxy's large halo. These are globular clusters -- tightly bound groups of stars that can often fend off cannibalism from larger, "bully" galaxies. Studying these surrounding clusters will prove helpful to astronomers in their pursuit to put the pieces of ESO 306-17's history together.

Researchers are also using this image to search for nearby ultra-compact dwarf galaxies. Ultra-compact dwarfs are mini versions of dwarf galaxies that have been left with only their core due to interaction with larger, more powerful galaxies. Most ultra-compact dwarfs discovered to date are located near giant elliptical galaxies in large clusters of galaxies, so it will be interesting to see if researchers find similar objects in fossil groups.


Story Source:

The above story is based on materials provided by ESA/Hubble Information Centre. Note: Materials may be edited for content and length.


Cite This Page:

ESA/Hubble Information Centre. "Bully galaxy rules the neighborhood." ScienceDaily. ScienceDaily, 21 March 2010. <www.sciencedaily.com/releases/2010/03/100304102159.htm>.
ESA/Hubble Information Centre. (2010, March 21). Bully galaxy rules the neighborhood. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2010/03/100304102159.htm
ESA/Hubble Information Centre. "Bully galaxy rules the neighborhood." ScienceDaily. www.sciencedaily.com/releases/2010/03/100304102159.htm (accessed October 24, 2014).

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