A challenge to cold and warm dark matter

John McKean

Dark matter forms a fundamental part of our Universe, yet we know very little about its properties. Although the large-scale structure of galaxies and clusters of galaxies in our Universe places some constraints on the nature of dark matter, it is on the smallest mass-scales (from a few million Solar masses to a few Jupiter-mass scales) that are proving to be the most informative. Since dark matter is not by definition luminous, studying its properties has proven to be very difficult. Therefore, astronomers use indirect methods that are sensitive to the presence of dark matter.

Figure: A generated representation of what the dark object could be. The best fitting model is a massive black hole (~0.3 million solar masses) that is embedded in an extended disk of dark matter with a size of about 140 parsecs. The mass profile of the object is shown as the black curve of the inset. Also shown are the results from other mass profiles tested with the EVN data, which include models that describe a globular cluster, a dark matter halo and a dwarf galaxy. Image credit: Simona Vegetti.

Link to the papers:

McKean et al. (2025) https://doi.org/10.1093/mnrasl/slaf039

Powell et al. (2025) https://www.nature.com/articles/s41550-025-02651-2

Vegetti et al. (2026) https://www.nature.com/articles/s41550-025-02746-w

Contact:

John McKean, University of Groningen, University of Pretoria, South African Radio Astronomy Observatory. Email: john.mckean@up.ac.za