Collaborative Research: Observing Cosmic Dawn with the Long Wavelength Array

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A short time after the Big Bang, the Cosmic Dawn emerged and featured the formation of the first stars, black holes, and galaxies. Neutral hydrogen gas dominated the Universe during this epoch and is now detectable in the radio bands through its redshifted 21-cm line, initially manifest as an absorption line in the cosmic microwave background. As the life cycle of the first stars ended and the first black holes formed, matter accreting onto the black holes produced X-rays, which heated the intergalactic medium (IGM). As the IGM was heated, the 21-cm line of the neutral hydrogen gas moved from producing absorption lines to emission lines until the gas was ionized during the epoch of reionization, thus removing the detectable signal.This two-year research project will employ a novel observing strategy to detect this redshifted 21-cm line signal using the existing first Long Wavelength Array station (LWA1) in New Mexico, which consists of 256 dual-polarization dipole antennas that are digitally combined to form multiple beams on the sky. While the time history of the absorption and emission features is imprinted on the all-sky radio spectrum, the observational challenge is to separate the approximately 100 mK signal from the dominant Galactic foreground emission. The investigators' strategy exploits the unique beam forming capability to remove calibration uncertainties that plague other instruments by simultaneously targeting science and calibrator fields. The investigators expect to their efforts to lead to the first detection of the 21-cm absorption signal at a redshift of z=25 that will open a new window on early star formation and the IGM.Educationally, as both institutions have high minority enrollment, this project will actively seek to involve underrepresented student groups, and it will fund a graduate student for two years and will provide opportunities for student training and mentoring in an interdisciplinary environment including principles of digital signal processing, software design, statistical analysis, model fitting, and astrophysics.