Universiteit Leiden

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Vici grant for research on the formation of galaxies

How do galaxies form? That is what astronomer Mariska Kriek will be researching in the coming years. She received an NWO Vici grant of 1.5 million euros to study galaxies in the early universe. ‘This research uses new and unprecedented observations from the James Webb Space Telescope (JWST). These allow us to finally understand how the galaxies in the near universe formed.’

A galaxy is a vast collection of stars, gas, dust, black holes and dark matter. To unravel how these form, we need to be able to look into the early universe. ‘We can study our Milky Way and nearby galaxies in detail,’ says Kriek. ‘But then we can only see what they look like now. It is difficult to deduce their origin from those observations.’

Because light has a finite speed, we can investigate the past when we look very far into the universe. ‘That way we can see what distant galaxies looked like when the universe was much younger.’ But this way of exploring entails two problems. ‘Distant galaxies are very faint which means we can see very little detail. In addition, the starlight we receive from these distant galaxies has shifted to infrared wavelengths. That is because the universe is expanding. As a result, the light waves stretch during their journey to our telescopes.’

Looking 8 to 12 billion years back in time

Both problems are now history thanks to the JWST. With its large mirror and infrared eyes, astronomers can look further into the universe than ever before. ‘The universe is now about 13.7 billion years old. With our programme, we will observe galaxies in the universe when it was only 1.5 to 5.5 billion years old. That means we are looking about 8 to 12 billion years back in time.’

One of the first images of the JWST.

The JWST has delivered many new, beautiful results in its first months. These already tell us much more about the evolution and formation of galaxies than we ever knew. Kriek will work with data from upcoming observations. ‘We will mainly look at galaxies in the early universe that are now no longer forming stars. So these galaxies seemed to have matured when the universe was very young. We want to understand why they formed so quickly and why they are now no longer forming new stars. In addition, these distant mature galaxies look different from the galaxies we see around us today. Therefore, we want to understand how these galaxies from the distant past continued to evolve with time.’

'No idea yet what we will find'

Kriek and her team will study these distant galaxies using deep spectra. ‘Spectra are a kind of fingerprint from which we can deduce many properties. With these, we dissect the light from distant galaxies into different wavelengths. They tell us more about the galaxies’ chemical composition, the stars' ages, and how fast the stars are moving in those distant galaxies.’

Kriek is extremely happy with the Vici grant. It will allow her to work with two postdocs and two PhD students on the new JWST data. ‘I am looking forward to receive and analyse the first data. We have no idea yet what we will find, so it is incredibly exciting.’

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