The Extragalactic Streams Group
Funded by Villum Fonden (project VIL53081) and by the European Commission (ERC starting grant: BeyondSTREAMS 101115754). The group's work focuses on what we can learn about the nature of dark matter from extragalactic streams through simulations, model-to-data comparisons, and observations from the Roman Space Telescope, Rubin, Euclid, and ARRAKIHS.
Sarah Pearson
group leader
Pearson recently returned to the Niels Bohr Institute at the University of Copenhagen after spending 10 years in the US, where she obtained her PhD degree in Astronomy from Columbia University in 2018, held a NASA Hubble Fellowship at New York University (2020-2023), and a Flatiron Research Fellowship at the Center for Computational Astrophysics (2018-2020). Pearson's research interests include galactic collisions, stellar streams, galactic bars, and dark matter. You can find a link to her publications here and details on her research interests here.
Khyati Malhan
Postdoc
Malhan's research interests include Galactic archaeology, dark matter, and he is best known for his work on the stellar streams of the Milky Way. His style encompasses and combines observations and data analysis (e.g., Gaia, APOGEE, LAMOST), running N-body simulations of stellar systems, and analyzing large-scale cosmological simulations (e.g., Illustris, TNG). He obtained his PhD from Strasbourg Observatory between 2015-18, followed by a postdoc at Stockholm University from 2018-21, and a Humboldt postdoc fellowship at MPIA, Heidelberg from 2021-23. You may find his publications here.
Sirui Wu
PhD student
Wu joined the group in September 2024 after obtaining his master's degree in astrophysics from Sun Yat-sen University in China. Wu's research interests focus on constraining dark matter distributions with various methods such as stellar streams, galaxy dynamical analysis, and gravitational lensing. He is also interested in the applications of machine learning in astronomical data analysis. You can find his most recent publications here.
Julie Kiel Holm
Master's student
Holm is finishing her master's degree at UCPH, where her work has previously focused on astrophysical transients and multimessenger astrophysics. Her master's thesis concerned the theoretical prediction of neutrino spectra from gamma-ray bursts, and previous work has been centred on the sodium content of the circumstellar media of supernovae. Now she instead shifts her focus to exploring the field of dark matter and galactic dynamics through the study of stellar streams. Join our group!
The Extragalactic Streams group is hiring postdocs and PhD students for a 2025 start date. The call is closed and we expect to conduct interviews in Decemeber 2024 and January 2025. Please contact HR with any questions. In addition to open positions in our group, there are also other opportunities to work at U. Copenhagen (e.g. the DAWN and DARK Postdoctoral Fellowships, and the Marie Skłodowska-Curie Actions fellowship). Please reach out if you are interested in working with us. For bachelor's or master's students enrolled at the University of Copenhagen, please get in contact about potential projects for the fall 2025 semester at sarah.pearson (at) nbi.ku.dk.
Prospective students can find the group research expectations here>>.
Former members
Daniel A Bobruk (summer student)