These observations reveal unexpected dark matter behavior

What if dark matter interacted with itself? A new study on the "El Gordo" galaxy cluster suggests that dark matter might be collisional, thus challenging the current standard model. This discovery could transform our understanding of the Universe.


Research led by Riccardo Valdarnini from SISSA, published in Astronomy & Astrophysics, has revealed that dark matter in the "El Gordo" cluster could be self-interacting. Using numerical simulations, the study analyzed this cosmic giant located seven billion light-years away.

The results show that the separation between the regions of maximum dark matter density and those of other mass components can be explained by the SIDM (Self-Interacting Dark Matter) model rather than the standard model.

This study supports the SIDM model, where dark matter particles exchange energy through collisions, which has significant implications in astrophysics. "El Gordo," with its unique characteristics, serves as an excellent laboratory to study these interactions.

Valdarnini explains that, according to the standard model, the behavior of collisional gas differs from that of galaxies and dark matter during cluster mergers. However, the SIDM model predicts a separation of dark matter centroids from other components, a phenomenon observed in "El Gordo."

Through N-body/hydrodynamic simulations, Valdarnini demonstrated that the separations between the different mass centroids of "El Gordo" can be explained if dark matter is self-interacting. This indicates a collisional behavior of dark matter in high-energy cluster collisions.

However, the measured values for SIDM interactions are higher than the current limits, suggesting that existing SIDM models are not perfect. The physical processes involved in dark matter interaction are more complex than previously thought.