Freaky galaxies

Sombrero galaxy

Sombrero galaxy

In recent galaxy evolution news, a 10 billion year old ultra compact dwarf galaxy was discovered using the 10-metre Keck II telescope on Mauna Kea in Hawaii, and studied with x-ray detection from Chandra. For comparison, the universe is only about 13.7 billion years young, plus or minus 0.13 billion years (see also here for a discussion on age. Not quite the oldest galaxy. It is apparently part of the globular cluster system associated with the Sombrero galaxy.

There are apparently two possibilities. This was a full blown galaxy that got stripped down. Considering that this was formed during the relatively early stages of the universe, which was a fairly violent and energetic era, that seems to be a real possibility. What I think is more likely (and from the article, Duncan Forbes, from Swinburne University seems to agree from the evidence he’s seen) is that it is a massive star cluster that formed early on. The arxiv paper can be found here. The evidence discussed in the paper that suggests this is not a stripped galaxy seems to be a failure to find tidal extensions or tails that would have come about from interactions from other massive objects. There would have to have been time for these tell tail signs to be wiped out indicating that any stripping would have had to occur a very long time ago. That would seem to make it somewhat unlikely.

What is also interesting about this ultra compact dwarf is that its dynamics shows a lack of dark matter dominance. It would be interesting to explore this a bit further to see what this says about dark matter distribution and its role in galactic evolution.


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