Research Overview
How do galaxies form and evolve across cosmic time?
Galaxies change their structure, chemical composition, and star formation properties over the time of more than 13 billion years, from the Big Bang to the present day. During their evolution, they also impact their larger surrounding environment. For example, they cause the Hydrogen in the Universe to transition from an neutral to an ionized state (the so called Epoch or Reionization). Constraining and measuring the changes in the galaxy populations as a function of time, understanding the physical reasons that cause these changes, and inferring the impact of galaxies on their surrounding are current hot topic in astrophysics.
Due to the large time scales over which stars form (millions of years) and galaxies change (100 million of years), it is not possible to follow a single galaxy through cosmic time. Instead, we study populations of various galaxies at different times. With empirical and analytical models and with the help of extensive computer simulations, we are able to connect these different snapshots in time to construct a coherent picture of galaxy formation and evolution.
My research focuses on understanding the early formation and evolution of galaxies, specifically focusing on their chemical composition, gas and dust abundances, and star formation properties. In order to characterize the detailed properties of galaxies, photometric and spectroscopic observations at various wavelengths are necessary. I am leading several large international collaborations using various cutting-edge telescope facilities to do this (see my current Research Projects). I combine these observations with novel analysis methods such as cloud-based science platforms and machine learning / AI approaches.
Below, I summarize the cornerstone that shape the research of my group.
How do the First Galaxies Form?
New JWST observations suggest that galaxies existed close to 200 million years after the Big Bang (that corresponds to a redshift z = 16). Some of the galaxies are extremely massive and may challenge our theoretical understanding of how structure in the early Universe is grown. Furthermore, there is growing evidence that accreting, super massive black holes are abundant at early times. How did these galaxies came into being and how did these early black holes grow and co-evolve with their hosts? With multi-wavelength photometry and spectroscopy, we find and characterize these early systems and their star formation history. Through the study of their environment and clustering on the sky, we constrain their impact on reionizing the early Universe.
How do Galaxies Evolve?
Galaxies in the early Universe are rather different compared to modern galaxies (such as our Milky Way) in terms of their structure and chemical composition. They are more turbulent, highly star forming, and lower in metal and dust content. So, how do these properties evolve over time and why? By deep-diving into the resolved details of early galaxies and their chemical compositions, we can inform models of how and when these properties change.
What is the Fate of Galaxies?
While galaxies in the early Universe are highly star forming, their star formation rates drop significantly at later times. What causes the star formation to change and eventually to cease? With theoretical models and observations we constrain the burstiness of star formation in early galaxies. Using large-area surveys, we aim to find rare occurrences of the first "quiescent" galaxies and study what causes them to cease star formation.
Big Data and AI
The large data sets provided by current and next-generation wide-field surveys open a new parameter space in galaxy evolution and time domain studies. To use these data, novel analysis methods based on machine learning and science platforms have to be introduced. With cross-disciplinary efforts involving computer scientists, we conquer the enormous data flow using innovative techniques and infrastructure.
The Next Generation of Facilities?
New and updated facilities are needed in the ever-changing scientific landscape. New infrastructure such as science platforms allow everyone to analysis Big Data. New telescopes allow us to cover missing wavelength gaps that will reveal more details on planets, stars, and galaxies. Strong involvement in next-generation facilities is a must. The research conducted by my group shapes new technologies to enhance our understanding of galaxy evolution.