Charting the history of reionization with radio observations of the early universe

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Dr. Jacobs is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at Arizona State University. The goal of the research is to detect evidence of the first stars, thought to be born sometime about 500 Million years after the Big Bang. These stars emitted intense radiation which burned away the universe's pervasive atmosphere of Hydrogen. As hydrogen accounts for three quarters of the normal matter in the universe, this last global cosmological process underpins much of what is known about cosmology and galaxy formation. However, observing this time period in ordinary star light challenges the world's premier telescopes due to the extreme distance and faintness of the early stars. The goal of this research program is to detect and characterize radio emission from intergalactic hydrogen before and during its ionization using two recently completed radio telescopes. Detecting and characterizing the predicted radio signature of this "Cosmic Dawn" was rated as a top priority by the astronomical community. This project will also support a student volunteer corps who will take a portable a planetarium to schools and who will be directly involved in developing elements for museum and planetarium facilities. These include a state of the art 3D planetarium theater, in the recently constructed Arizona State University astronomy building.Recent advances in digital technology allow the construction of very large arrays of antennae which provide the necessary sensitivity to detect radio emission from Hydrogen when the universe was only 300Mya old. Emitted at a wavelength of 21cm, the radiation is stretched by cosmological expansion to an observed wavelength of 1.5 to 3m depending on the time period under observation. Both the Murchison Widefield Array (MWA) and the Precision Array for Probing the Epoch of Reionization (PAPER) have been designed to observe these wavelengths at the necessary sensitivity and are constructed, in large part with funding from the National Science Foundation, far from interfering human radio emission; the MWA is in Western Australia and PAPER is in the Karoo desert of South Africa. Using both telescopes, Dr. Jacobs will compile a deep statistical measure of the amount of radiation coming from Hydrogen in the early universe. Portions of the work include performing observations, measuring and removing other bright interfering signals from other bright astronomical objects, and applying this new knowledge to building larger telescopes capable of directly imaging the early universe. These measurements of bright interfering signals will form a substantial, interesting, and compellingly beautiful image of the universe and provide a foundation data set for exhibits produced by the student corps created as a part of the project. The team of undergraduate students will have two goals: First to improve retention of astronomy and science education undergraduates and second to bring planetarium shows to traditionally underserved schools and tribal centers which cannot take advantage of other, more costly, programs.