Contrary to what is established by the standard model, dark matter may indeed be self-interacting. This was the conclusion of a piece of research published in Astronomy & Astrophysics and conducted by Riccardo Valdarnini of SISSA’s Astrophysics and Cosmology group. Using numerical simulations, the study analyzed what happens inside “El Gordo” (literally “The Fat One” in Spanish), a giant cluster merger seven billion light years away from us.
Research findings suggest Collisional Dark Matter as an explanation for the phenomena observed in ‘El Gordo’
In order to explain his findings and validate the SIDM models, Valdarnini used a large set of so-called N-body/hydrodynamical simulations. Thus, he carried out a systematic study aimed at reproducing the observational features of “El Gordo.”
“The most significant result of this simulation study is that the relative separations observed between the different mass centroids of the ‘El Gordo’ cluster are naturally explained if the dark matter is self-interacting,” states Valdarnini.
“For this reason, these findings provide an unambiguous signature of a dark matter behavior that exhibits collisional properties in a very energetic high-redshift cluster collision. There are, however, inconsistencies, as the SIDM cross section values obtained from these simulations are higher than present upper limits, which are of order unity at cluster scales.
“This suggests that present SIDM models should be considered as only a low order approximation, and that the underlying physical processes that describe the interaction of dark matter in major cluster mergers are more complex than can be adequately represented by the commonly-assumed approach based on the scattering of dark matter particles.
“The study makes a compelling case for the possibility of self-interacting dark matter between colliding clusters as an alternative to the standard collisionless dark matter paradigm.”
www.aanda.org/articles/aa/full_html/2024/04/aa48000-23/aa48000-23.html