Andrew Benson

Caltech

"What I cannot create, I do not understand": A galaxy builder's toolkit

Abstract: Galaxy formation is an intricate process and observations of galaxies have complex relations to the underlying physical quantities. I will argue that to prove we have understood the physics of galaxy formation requires that we be able to create model universes which are indistinguishable from our observed Universe. I will describe a recently developed toolkit, Galacticus (http://sites.google.com/site/galacticusmodel), which aims to meet this challenge by providing a coherent framework within which to compute expectations about galaxies across all wavelengths, mass scales and redshifts. To demonstrate the flexibility and power of this approach I will highlight recent work on building virtual Universes for the Caltech-Cornell Atacama Telescope project.

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Prasenjit Saha

University of Zurich Institute for Theoretical Physics

"Relativity and the Galactic-center Stars"

Abstract: The S stars near the Galactic center reach speeds of a few percent of light at pericenter, which suggests that during pericenter passage, the redshifts of these stars would contain signatures of general relativistic effects: time dilation, space curvature, and frame dragging. I will explain what the relativistic signatures are, and speculate about whether the observational difficulties could possibly be overcome.