CfA Colloquium Schedule Fall 2013
 7 November 2013

7 November 2013

Speaker: Tommaso Treu (UC Santa Barbara)

Title:Studying Dark Energy and the Dark Ages with Gravitational Lensing

Abstract: I will describe two observational projects that exploit the power of strong gravitational lensing to address some of the most fundamental questions in galaxy formation and evolution and cosmology. The first project is concerned with the nature of dark energy. I will show that strong gravitational lenses where the background source is variable in time and the foreground deflector is a massive galaxy act as cosmic "standard rods". I will illustrate recent advances in modeling techniques and data quality enabling a 7% measurement of distance from a single gravitational lens. Results from just two systems yield constraints on the equation of state of dark energy and flatness comparable and complementary to those obtained with the best probes. The second project is concerned with identifying the first galaxies at z > 7, around the epoch of cosmic reionization. Even though large samples of candidate z~8 galaxies are now known from HST imaging, spectroscopic confirmation is still lacking. This suggests a dramatic change of the conditions of the interstellar and intergalactic medium at these redshifts. I will discuss the current state of affairs and my plan to make progress by exploiting lensing magnification by foreground clusters of galaxies in combination with a large deep Hubble Space Telescope spectroscopic survey (GLASS).


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