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Astronomy Tea Talk

Monday, October 21, 2013
4:15pm to 5:00pm
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Cahill, Hameetman Auditorium
"Galaxy Zoo, Barred Galaxies and Secula Evolution"
Edmund Cheung, USCS,

Observations have shown that there is a connection between the presence of a bar and the properties of a galaxy. In a parallel effort, simulations have shown that this connection is consistent with the theory of bar-driven secular evolution. But observational evidence of bar-driven secular evolution has been sparse. In this talk, I use the Galaxy Zoo 2 dataset to look for evidence of this secular evolution. My sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 ± 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role
of bars in disk galaxy evolution. I characterize bars by the bar likelihood, the likelihood a bar is present in a given galaxy, and the bar length. These two bar properties show interesting correlations with the specific star formation rate and the inner central structure of galaxies. Comparing these observations to state-of-the-art simulations of bar evolution, which include live halos and the effects of gas and star formation, reveals that trends are consistent with the predicted effects of gas content and bulges on bar formation and evolution. These results represent empirical evidence for secular evolution driven by
bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies, but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

For more information, please contact Luca Ricci and Dan Perley by phone at 626-395-2460 and 626-395-3734 or by email at and