Thursday, January 18, 2007

Hobbit Galaxies

According to this story from the SDSS has found 8 more dwarf galaxies in the local group. Seven of which appear to be satellites of the Milky Way, these seven galaxies, all of which are very faint and diffuse appear to be essentially old. The one new galaxy which is not thought to be bound to the MW appears to still be forming stars and to have a significant reservoir of neutral hydrogen with which to form more stars.

This is all very interesting because it has implications for one of the big problems of modern cosmology, the so called "missing satellite" problem. This is the observation that cosmological simulations of structure formation in a dark-energy, dark matter dominated Universe seem to predict many more small satellite galaxies around larger galaxies like the MW than we see. If however these galaxies do exist and they are simply very faint and hard to see as the SDSS results imply, then there isn't any problem at all. Seeing as the SDSS only covers about an eighth of the sky, and doesn't see very faint things, it does imply that there should be many more of these galaxies left out there to be found. I think a cottage industry of trying to find these things is probably about to spring up.

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