CANCELLED
Astronomy Seminar Series
Brenda Frye, University of Arizona
Galaxy clusters as astronomical tools generally offer two advantages: to boost the brightnesses of objects in the background, and to study the dark matter in the lens. We can now introduce a third use: to unveil properties of the underlying dark matter by the detection of caustic crossing events which can yield magnification factors of 10,000 or more. We review the approach to detect a new set of massive objects such as galaxy clusters by their rest-frame far-infrared colors (and not by the Sunyaev-Z'eldovich effect). We move on to present Hubble Space Telescope WFC3-IR imaging in the fields of six classical giant arcs discovered using a combination of Planck and Herschel space facilities. We construct lensing models from the many examples of image multiplicities, and compare our results with galaxy over-densities identified by more conventional methods. We conclude with a discussion on the emerging field of caustic crossings.
Prof. Frye is making a concerted effort to understand how galaxies form and evolve in the universe. She has chosen to take the approach of gravitational lensing, which is good for two reasons: (1) to boost the sizes and brightnesses of the galaxies in the background, and (2) to study the dark matter in the foreground lens. She observes galaxies lensed by foreground galaxy clusters in order to measure the physical properties of these otherwise too-faint sources, and to study the cluster caustics.
In a novel approach, she has also identified high-redshift galaxy cluster lenses (z = 2 - 3), by their far-infrared colors using Planck Telescope and Herschel Space Observatory. Taken all together, this work has resulted in the discovery of some of the most distant galaxies and galaxy overdensity regions, and is leading to a better understanding of the evolution of massive structures.
Dr. Frye is an Assistant Professor at the University of Arizona, and before that was also a Professor the University of San Francisco, and Dublin City University in Ireland.