COLDz II: Ultra-Deep Imaging of the Cold Gas History of the Universe

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This project will continue the most comprehensive program to measure the cold gas history of the universe with the NSF's Karl G. Jansky Very Large Array (VLA). The goal of this project is to complete the picture of galaxy formation and evolution throughout cosmic history. Cold gas is the fuel for the formation of stars in galaxies. It holds the key towards understanding the buildup of stars since early epochs. This extension of the VLA program will provide measurements across approximately eleven of the 13.7 billion years since the Big Bang. With more than ten times longer exposure times, it will lead to the identification of unprecedentedly faint galaxies. In addition to being published in academic journals, the findings of this program will be publicly disseminated to children, young students, and general audiences. It will directly address one of the highest-priority science objectives of the current decade by revealing how galaxies like our Milky Way and its ancestors grew to become what they are today. This project focuses on a comprehensive analysis of the second phase of the NSF's Karl G. Jansky Very Large Array (VLA) CO Luminosity Density at High Redshift (COLDz) survey, with the principal goal to systematically measure the volume density of molecular gas through cosmic times, i.e., the fundamental driver of star formation and stellar mass buildup in galaxies since the Big Bang. Motivated by tensions between our current observations and state-of-the-art modeling efforts, the proposed expansion will provide order-of-magnitude improvements over the initial measurements. The project will provide a solid foundation for motivating key technological developments for future US-based flagship facilities, such as the ngVLA (previous research by this group motivated one of its key science goals). Compared to previous work, this project will investigate the contribution of fainter galaxies to the gas density over a more complete coverage of cosmic history, including a deeper understanding of statistical and systematic uncertainties for the derivation of physical quantities. A diverse set of hands-on education, research training, and outreach events targeting young children, students at all levels, and the public, including underprivileged communities, will broaden the impact of this research.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.