A possible challenge for cold and warm dark matter
Abstract Measuring the density profile and mass concentration of dark-matter haloes is a key test of the standard cold dark matter paradigm. Such objects are dark and thus challenging to characterize, but they can be studied via gravitational lensing. Recently, a million-solar-mass object was discovered superposed on an extended and extremely thin gravitational arc. Here we report on extensive tests of various assumptions for the mass density profile and redshift of this object. We find that models that best describe the data have two components: an unresolved point mass of radius ≤10 pc centred on an extended mass distribution with an almost constant surface density out to a truncation radius of 139 pc. These properties do not resemble any known astronomical object. However, if the object is dark matter dominated, its structure is incompatible with cold dark matter models but may be compatible with a self-interacting dark-matter halo where the central region has collapsed to form a black hole. This detection could thus carry substantial implications for our current understanding of dark matter.
Authors
- C. D. Fassnacht (ORCID: https://orcid.org/0000-0002-4030-5461)
- Devon Powell (ORCID: https://orcid.org/0000-0002-4912-9943)
- Cristiana Spingola (ORCID: https://orcid.org/0000-0002-2231-6861)
- D. Massari (ORCID: https://orcid.org/0000-0001-8892-4301)
- Giulia Despali (ORCID: https://orcid.org/0000-0001-6150-4112)
- Simon D. M. White (ORCID: https://orcid.org/0000-0002-1061-6154)
- Simona Vegetti
- John P. McKean
Institutions
- University of Groningen (NL)
- Max Planck Institute for Astrophysics (DE)
- Istituto di Radioastronomia di Bologna (IT)
- South African Radio Astronomy Observatory (ZA)
- Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (IT)
- Osservatorio di Astrofisica e Scienza dello Spazio
- University of Pretoria (ZA)
- University of California, Davis (US)
- National Institute for Astrophysics (IT)
- University of Bologna (IT)
Publication Details
- Journal
- Nature Astronomy
- Published
- 2026-01-05
- DOI
- https://doi.org/10.1038/s41550-025-02746-w
- Citations
- 2
- Primary Topic
- Dark Matter and Cosmic Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 55.92
Funders
- European Commission
- National Research Foundation
- Ministero dell’Istruzione, dell’Università e della Ricerca
- Max-Planck-Gesellschaft
- Ministero degli Affari Esteri e della Cooperazione Internazionale