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Jorryt Matthee - Identifying the origins of galaxy formation

Cosmic mist, first-generation stars and state-of-the-art computer simulations made clear that distant galaxies are much more than just simple dots in the sky. By investigating galaxies from the past, astronomer Jorryt Matthee from Leiden Observatory hopes to answer questions about the origin of galaxies, such as our own Milky Way.

Distant galaxies

Using the largest telescopes in the world, Matthee discovered several rare, bright galaxies in the distant Universe. The light from these stars has taken so long to reach us, that what we are seeing is actually in the past. Researchers therefore use these galaxies to look far back in time and unravel questions about the origin of stars and black holes. ‘After finding these distant galaxies, I discovered specific characteristics that were not observed in distant galaxies before’, Matthee says. Looking back 13 billion years in time, he discovered that distant galaxy CR7 is much more complex than his team initially thought. He hoped to find first-generation stars, containing nothing more than hydrogen and helium. However, after deep observations with the ALMA telescope, Matthee discovered that traces of carbon are already present in the developing galaxy. Matthee also was the first to find direct evidence for the dispersing of cosmic mist around galaxies in the early Universe.



Besides observing distant galaxies, Matthee also used state-of-the-art computer simulations to follow the formation and evolution of simulated galaxies through time. ‘This is impossible in real observations, as they only provide us with a single snapshot of a galaxy’, he explains. Matthee uncovered why the masses and growth rates of galaxies differ and that these differences can largely be traced back to smaller differences in the very early Universe. Combining his observations with the computer simulations, Matthee hopes to unravel the mysteries of galaxy formation.

Impossible to find?

At first, scientists did not believe that bright but very distant galaxies existed. Their disbelief was an extra challenge for Matthee: ‘When I proposed for usage time on several telescopes to search for these galaxies, I was not awarded time, as the allocation committee deemed finding them was impossible.’ Matthee then used a large compilation of old datasets to show that the galaxies exist anyway. Now, other teams around the world are confirming the findings, pursuing similar observational strategies. This has already resulted in the discovery of other exciting galaxies, which Matthee and other researchers now study in more detail.

New understandings

These new insights make it necessary to revise the way distant galaxies are observed. ‘Simultaneously with other teams, we are beginning to understand that galaxies - even those in the very distant Universe - can no longer be treated as simple dots of light, ignoring the resolved structure we see. This impacts detailed strategies on how to obtain future observations of such galaxies, especially those that we will perform with the upcoming James Webb Space Telescope.’

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