Galaxies are the basic building blocks of the Universe. Although new stars are continuously forming in our home galaxy, the Milky Way, most stars are found in giant elliptical galaxies. Such galaxies, which have an oval shape, stopped forming stars billions of years ago.
Sune Toft, Professor of Cosmology and Extragalactic Astrophysics at the Niels Bohr Institute in Copenhagen, is revealing how these galaxies formed, evolved and died – crucial to understanding the Universe and everything we see around us.
His research investigated the origin of elliptical galaxies to see whether different types of extreme galaxies are actually phases of a massive galaxy’s evolution.
The research team studied starburst galaxies, which have an unusually high rate of star formation and are thought to be the early phase of the giant elliptical galaxies. Over five years, the team observed starburst galaxies at different wavelengths, studied individual galaxies in depth, and analysed statistical studies of millions of galaxies to discover more about the structure, shape, dynamics, star formation properties, gas contents and other characteristics of different galaxy populations.
The results show that the largest elliptical galaxies can be traced back to less than a billion years after the Big Bang, when they formed in enigmatic starbursts and evolved until star formation was quenched.
These findings are now a widely accepted model of the evolution of massive galaxies, supported by other studies.
New generations of astronomical surveys using ALMA – the largest telescope in the world – and the James Webb Space Telescope will further explore the model.
The team also developed a photometric catalogue of their research, which they believe could be a benchmark for galaxy evolution studies over the next decade.
The project has also paved the way for a major centre of excellence called the Cosmic Dawn Center (DAWN) at the Niels Bohr Institute and DTU Space in Denmark. DAWN focuses on uncovering how and when the first galaxies, stars and black holes formed.