CAREER: Linking the IGM and Galaxies Near Reionization

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Thirteen billion years ago the Universe was a very different place. Galaxies were just beginning to form from the matter created in the Big Bang, and the intense radiation emitted by these galaxies was burning away the fog of hydrogen gas permeating deep space. In less than one billion years the fog had cleared, and the young galaxies lived in a Universe where ultraviolet radiation could travel freely through space. This transformation of the gas in deep space is known as "cosmic reionization", and it was a landmark event in the early Universe. By studying reionization we learn not only about the history of matter in the Universe, but about the formation of the first galaxies. The goal of this project is to connect the changes we see happening in deep space during reionization to the characteristics of the first galaxies themselves. How can we combine observations of galaxies and deep space to learn more about this era of cosmic history? What imprints on the Universe does reionization leave behind? The PI will use the world's largest telescopes to directly probe both galaxies and intergalactic gas over the same regions early in cosmic history. The observations will be combined with state-of-the art computer modeling to better understand how cosmic reionization occurred and the ways in which it impacted early galaxies and the matter in deep space. Building on this research, the PI will integrate his observational expertise into local high-school and undergraduate education. A key element of this program will be the creation of a campus observatory at UC Riverside. This will be one of the few such facilities in the country to offer spectroscopy, one of the most broadly used techniques in science and industry, and will be used to promote STEM engagement among underserved groups in Southern California.Roughly one billion years after the Big Bang the Universe underwent a global transformation. The first galaxies formed in a Universe filled with dark matter and cold, neutral gas. As the radiation from these galaxies permeated deep space, however, the gas was ionized and heated, rendering the Universe transparent to ultraviolet photons. Thirteen billion years later the gas in deep space is still highly ionized. The early transition from neutral to ionized was therefore the last phase transition of matter in the Universe. Known as "reionization", this transformation was a key event in cosmic history. The goal of this proposal is to determine when and how reionization occurred by simultaneously studying the gas in deep space and the galaxies embedded within it. The PI will use the word's largest telescopes to study galaxies (via wide-field imaging) and intergalactic gas (via absorption-line spectroscopy) in the same cosmic volumes during and after reionization. Spectroscopy will also be used to study the gas in and around galaxies themselves. These will be the first observations to directly connect the evolving conditions in deep space to the sources driving the evolution. By further combining data with state-of-the-art modeling, this project will provide a better understanding of how cosmic reionization occurred and the ways in which it shaped early galaxies and intergalactic matter throughout the Universe. Building on this research, the PI will integrate his observational expertise into local high-school and undergraduate education by creating a campus observatory at UC Riverside. This will be one of the few such facilities in the country to offer spectroscopy, one of the most broadly used techniques in science and industry, and will be used to promote STEM engagement among underserved groups in Southern California.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.