Thursday, October 19, 2006, Pratt Conference Room at 12:30 pm
Galaxy Groups in DEEP2: Implications for Cosmic Evolution
Mr. Brian Gerke (UC Berkeley)
| Groups and clusters of galaxies, as the largest, most recently formed objects in the universe, carry much information about the recent history of the cosmos. By studying these systems at a variety of epochs, it is possible to reconstruct both the evolution of clusters and the history of large-scale structure formation. Such studies provide important constraints on theories of galaxy formation and on cosmological parameters. With the recent completion of the DEEP2 Galaxy Redshift Survey at z~1, it is now possible to perform detailed studies of galaxy groups and clusters over a wider redshift range than ever before. In this talk I will present recent results suggesting that, at the DEEP2 epoch, galaxy groups had *only recently* become suitable environments for shutting off star formation in galaxies. I will also present evidence that DEEP2 groups are underluminous in the X-ray band, when compared with local systems. Finally, I will describe an ongoing project to compare the DEEP2 group population to the local sample detected in the 2dFGRS. This work will allow new tests of galaxy-formation theory by probing evolution in cluster mass-to-light ratios. It will also permit new constraints on cosmological parameters by measuring the evolution of the group abundance between z~1 and the present day; in particular, this study should provide the first-ever constraint from cluster counts on the dark energy equation of state parameter. |
