Leveraging the Hobby Eberly Telescope Dark Energy Experiment to Understand Lyman-alpha Emission, Galaxy Evolution, and Reionization

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Observations have shown that the physical conditions in distant galaxy interstellar media (ISM) are changing, but the physical cause remains unknown. This project uses a soon-to-exist spectroscopic sample of galaxies showing Lyman alpha emission, which is an excellent probe of ISM geometry and kinematics, to measure the detailed physical properties of the ISM in these galaxies. It will also measure the contribution of Lyman alpha emitting galaxies (LAEs) to star formation. These results are critical to understanding the epoch of reionization. The project integrates research with education by involving ten or more UT Austin students per year in research related to the source of the data, the Hobby Eberly Telescope Dark Energy Experiment (HETDEX). It also impacts secondary school students nationwide through two residential teacher workshops at McDonald Observatory, and reaches millions by creating one StarDate Radio show each year.The work will constrain the physical mechanisms which promote the escape of Lyman alpha emission from galaxies during the peak epoch of cosmic star formation. Data for the first 300,000 spectroscopically confirmed LAEs from HETDEX will be combined with new extensive multi-wavelength imaging to i) measure the detailed evolution of the Lyman alpha luminosity function; ii) understand the physical properties which promote Lyman alpha escape; iii) measure the star-formation rate density contributed by LAEs; and iv) calculate the faint-end slope of the ultraviolet luminosity function for active galactic nuclei (AGN) to distinguish evolutionary trends and evaluate AGN contributions to reionization. Stellar population modeling of detailed physical properties will measure the evolution of the global escape of Lyman alpha emission, and the physical causes behind this evolution, and provide key data to constrain theoretical models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.