Ivelin GeorgievForskningsassistent

Within its first billion years, the Universe underwent a remarkable transformation, evolving from being cold and dark to hot and full of light. This dramatic change was driven by the formation of the first generation of stars and galaxies, which illuminated and ionised the opaque medium between them. We refer to this period as the Epoch of Reionization.

This pivotal era is defined by how the ultraviolet light from the earliest galaxies altered the state of hydrogen, the most abundant element in the universe, in the intergalactic medium. Neutral hydrogen atoms have a unique property: they emit radiation at a unique wavelength of 21 cm. This signal can be detected on Earth using advanced radio telescopes, such as the LOFAR and the Square Kilometre Array, currently under construction in remote parts of Australia. Studying how the 21 cm signal evolves over time provides a direct window into the conditions of the early Universe.

My research explores how the 21-cm signal can reveal the properties of the first light sources and how combining it with other observations of the intergalactic medium can deepen our understanding of the astrophysics of the first stars and galaxies as well as the fundamental nature of the Universe.