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View Full Version : Galaxy Growth Not Always Result of Violent Collisions



Fraser
2010-Oct-13, 06:10 PM
Until recently, it was thought the galactic equivalent of a motorway pile-up was the only way galaxies got bigger. But startling new evidence from a European team of astronomers suggests that violent galactic collisions are not the only way that galaxies evolve and grow, and instead there seems to be something else happening that has [...]

More... (http://www.universetoday.com/75626/galaxy-growth-not-always-result-of-violent-collisions/)

trinitree88
2010-Oct-15, 02:52 PM
Until recently, it was thought the galactic equivalent of a motorway pile-up was the only way galaxies got bigger. But startling new evidence from a European team of astronomers suggests that violent galactic collisions are not the only way that galaxies evolve and grow, and instead there seems to be something else happening that has [...]

More... (http://www.universetoday.com/75626/galaxy-growth-not-always-result-of-violent-collisions/)
http://arxiv.org/PS_cache/arxiv/pdf/1010/1010.2534v1.pdf
Fraser. Interesting. original paper....see:

matt.o
2010-Oct-15, 10:38 PM
I don't see how they can rule out mergers here. For instance, it has been shown by Kewley et al (2006), and also Ellison et al. (2008) that close pairs of galaxies (i.e. those likely to merger in the future) have lower gas-phase metallicities than comparable galaxies which do not have a close partner galaxy. This indicates that the interaction between the two galaxies drives lower metallicity primordial gas to the centres of the galaxies. This is confirmation of the predictions from merger models (Mihos & Hernquist 1994,1996 or Barnes & Hernquist 1996) which show that during a merger the effect of the interaction causes the gas to lose angular momentum and thus be funneled to the centre.

So while this study finds low metallicity in the galaxy centres, I am not sure their interpretation that this is a "cold flow" is the only one.