Research Overview
How did our Milky Way and its 400 Billion Stars, many with Planetary Systems, form?
How did galaxies and stars evolve their structure and chemical compositions across cosmic time?
These are some of the most fundamental questions in astrophysics - and some of the biggest questions of humanity: Where do we come from?
My research focusses on the study of how galaxies build up their chemical composition, mass, and structure and how their environments evolved across 13 billion years of cosmic time to become the places we live in today... including our own solar system.
See my research projects to learn more about the research of my group.
First Galaxies in Our Universe
Observations with the James Webb Space Telescope (JWST) show that galaxies existed less than 200 Million years after the Big Bang, the birth of our Universe 13.7 Billion years ago.
The radiation emitted by the young stars in these galaxies is so strong that it ionized the neutral hydrogen around them. This time is called the Epoch of Reionization.
With the first stars forming, the galaxies are being enriched with metals and dust. Recent observations with the JWST also show that their central super massive Black Holes grow via the accretion of gas and stars.
Early Structure Formation and the Most Massive Galaxies
Dark matter builds the backbone of structure formation in the early Universe. Dark matter attracts gas through gravity. Galaxies assemble in the dense knots of this "cosmic web".
The most massive galaxies form in overdense regions and as part of the most massive galaxy clusters. Their formation is still a mystery.
The clustering (hence most massive galaxies) define key cosmological parameters: the expansion rate and curvature of our Universe.
Chemical Enrichment of Early Galaxies
Galaxies in the early universe are metal poor and chemically pristine. They get metal enriched as soon as the first stars explode as supernova.
In addition to chemical enrichment, the galaxies' shapes change from dispersion dominated (turbulent) to rotation dominated (disk galaxies like our Milky Way).
Understanding the processes and timeline of these changes are key to understanding galaxy evolution. The first 1-2 billion years of cosmic time are crucial for these studies.
The only way to understand a galaxy as a whole is to observe the full electromagnetic spectrum - from ultra-violet to infrared light.
The Fate of Galaxies
About 10 billion years ago, galaxies significantly transformed: their star formation ceased. While galaxies formed many 100 stars per year, their star formation rates drop to just a few.
We call this stage the "quenching of star formation in galaxies" and there are several methods to do so.
Large samples and ingenious methods are necessary to find the emergence of these quiescent galaxies... and to understand which processes are dominant.
Combining Observations, Computer Simulations, and AI
In our research, we combine observations with state-of-the-art computer simulation models and Artificial Intelligence (AI).
With many terrabytes of data being produced by current observatories, we have to deploy fast AI methods to find correlations and relations... and to find rare phenomena that reveal the mysteries of our Universe.
Simulations enable us to better understand the physical processes in galaxies, stars, and our solar system... we can "play" with the Universe to understand what causes the observed correlations.
New Observatories
We have learned much so far about our Universe and where our Milky Way, planetary systems, and ourselves are coming from.
But with every step forward, more questions arise. There are still many physical processes that we do not understand, such as the nature of Dark Matter, the early formation of Black Holes, and the details of the feedback processes that shape the galaxies' history and future.