KIPAC Seminar: One, Two, Three... Infinity: Unveiling the Physics of Early Galaxies and Their Collective Impact at Cosmic Dawn

Abstract: Cosmic Dawn, broadly defined here as the first billion years of cosmic time (z>6), was the era when the first galaxies emerged, grew, and began to transform the young Universe on scales far beyond their own. Within individual galaxies, the buildup of stars and metals was governed by the complex and highly dynamic physical processes of star formation and stellar feedback. At the same time, the growing population of these early luminous objects affected the intergalactic medium and left large-scale signatures in cosmic radiation backgrounds, from the CMB to line intensity mapping observables like the 21 cm line of hydrogen. In this talk, I will highlight recent progress in theoretically understanding these two sides of the problem. Drawing on insights from high-resolution galaxy formation simulations, together with the emerging detailed view of the earliest galaxies revealed by JWST, I will show how early low-mass galaxies likely evolved in a highly bursty regime, with halo-scale turbulent gas and efficient feedback shaping their internal structure, star formation, and observable properties. I will then zoom out to discuss how statistical studies of galaxies and cosmic backgrounds open a complementary window onto the first galaxies through their collective imprint on processes such as cosmic reionization, which will be probed by large-scale surveys with SPHEREx, Roman, and SKA. Together, these multi-scale perspectives offer a powerful framework for understanding how the first galaxies formed and how they collectively shaped the landscape of Cosmic Dawn.