Hamsa Padmanabhan (Université de Genève)

Hamsa Padmanabhan Colloquium: Deciphering Cosmic Dawn: A Conquest of the Final Frontier

Kensington

Abstract

I will begin with a broad-based introduction to some of the big open questions in cosmology, and illustrate how upcoming experiments are well-poised to help answer them, especially at the Cosmic Dawn — the birth of the first galaxies in our Universe — widely believed to be the 'final frontier' of cosmological surveys today. This period — about a hundred million years after the Big Bang — is primarily accessible due to radiation from hydrogen, the most abundant element in the Universe, which emits at a wavelength of 21 cm, in the radio band. An exquisite investigation of the Cosmic Dawn will soon become possible with an emerging technique called intensity mapping (IM), which measures the integrated 21 cm emission from all sources, using large arrays of radio telescopes. A particular advantage of IM is that it provides a tomographic, or three-dimensional picture of the Universe, unlocking significantly more information than we presently have from galaxy surveys. I will overview the latest advances in research related to the evolution of hydrogen over 12 billion years of cosmic time, involving a novel data-driven framework to interpret current and future observations. This allows us to fully utilize our present knowledge of astrophysics in order to develop cosmological forecasts from IM. Apart from offering key insights into the nature of the first galaxies, this opens up the exciting possibility of testing theories of fundamental physics from the Cosmic Dawn.