Cosmology

Mapper of the IGM Spin Temperature (MIST), McGilL University, MSC work.

The epoch when the first stars in the Universe were born is an unsolved mystery in cosmology. Observations of this time are possible only through measurements of the redshifted 21-cm neutral hydrogen line, which are fundamental to our understanding of the Universe. The epoch known as the Cosmic Dawn can be probed by making 21-cm brightness temperature measurements averaged spatially across the sky, and the glow of the first stars is expected to cause a spectral absorption feature in this global signal. The EDGES experiment in 2018 reported an absorption feature centered at 78~MHz, with 0.5 K in depth; this absorption feature can be interpreted as being a detection of the global signal. RFI contamination, strong foreground emissions from the Milky Way (1000 K), ionospheric effects, and instrumental systematics are the biggest challenges to overcome experimentally, representing the primary limitations in obtaining a high-fidelity detection, and therefore new independent measurements are necessary. This thesis focuses on the development of MIST and Mini-MIST, new experimental efforts for detecting the global signal. These instruments will be installed in northern Chile and at the McGill Arctic Research Station (MARS), two of the most radio quiet sites on Earth. Because the measurement is limited by systematics, rather than statistical error, the primary challenge is precise design and characterization of MIST subsystems. The ultimate goal involves distinguishing the signal from Galactic foreground emission, which requires rigorously calibrating the instrument to approximately 1 part in 10,000. This thesis presents the development of a variety of MIST subsystems, including antenna design, readout electronics characterization, data acquisition, software development, and environmental monitoring of soil conductivity and permittivity.  With our efforts, MIST and Mini-MIST will provide invaluable, independent measurements of the Cosmic Dawn signal.  More details on the MIST website.