"Primordial galaxies" refers to the very first galaxies that formed in the early universe. These galaxies are considered ancient and hold important clues about the beginning of our universe. Full definition
That's because the properties, behavior, and fate of the first stars affected cosmic events that followed, such as the formation and distribution of primordial galaxies. (sciencemag.org)
«The previous record - holder was seen in the middle of the epoch when starlight from primordial galaxies was beginning to heat and lift a fog of cold, hydrogen gas,» explains co-author Rychard Bouwens from the University of Leiden, the Netherlands. (sciencedaily.com)
Whatever the cause of I Zwicky 18's strange history, its close resemblance to primordial galaxies offers a unique opportunity to study how stars acted in the early universe, something that normally can not be observed at such close range. (discovermagazine.com)