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Special Presentations

Probing the Physics of Galaxy Formation and Evolution in the Distant Universe

Presented by: Steven Finkelstein (The University of Texas at Austin)
Category: Special Interest   Duration: 1 hour and 15 minutes   Broadcast date: March 27, 2017
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Over the past two decades, the Hubble Space Telescope has frequently pushed back the high-redshift frontier, first through the epoch of galaxy assembly to z~4 and z~6 with the WFPC2/HDF and ACS/HUDF, and more recently through the epoch of reionization to z~8-10 with the HUDF09 and CANDELS WFC3/IR surveys. These latter surveys have allowed the construction of large samples (>1000) of galaxy candidates at z > 6, with which we have been using over the past few years to study galaxy evolution at early times. I will discuss the progress my research group has made with these data, including measuring robust constraints on galaxy colors, the evolution of the UV luminosity and stellar mass functions, and constraints from these distribution functions on the evolution of feedback effects in galaxies. We find that the faint-end slope of the luminosity function becomes quite steep by z~7, implying that galaxies fainter than our detection limit could dominate the reionization photon budget *if* galaxies exist far fainter than these surveys reached. Using data from the Hubble Frontier Fields project, we have recently directly observed that high-redshift galaxies do in fact exist (likely in great numbers) to at least 100 times fainter in luminosity than previously observed, close to the point where inefficient cooling is expected to suppress star-formation. Our results imply that galaxies intrinsically produced enough ionizing photons to accomplish reionization, though the escape fraction of these photons is still a major uncertainty. I will conclude with what I view are the most important topics for initial early-universe studies with the James Webb Space Telescope, and my longer-term vision for the future for this field with JWST, WFIRST, and LUVOIR.