The AIDA-TNG project: 3D halo shapes

Context. The shapes of dark matter halos can be used to constrain the fundamental properties of dark matter. In standard cold dark matter (CDM) cosmologies, halos are typically triaxial, with a preference for prolate configurations; however, including the full baryonic physics tends to make them more oblate. Aims. We focus on the characterization of total matter 3D shapes in alternative dark matter models, such as self-interacting dark matter (SIDM) and warm dark matter (WDM). These scenarios predict different structural properties due to collisional effects or the suppression of small-scale power. Methods. We measured the different halo component shapes – dark matter, stars, and gas – at various radii from the center in AIDA-TNG (Alternative Interacting Dark Matter and Astrophysics – TNG), which is a suite of high-resolution cosmological simulations built upon the IllustrisTNG framework. The intent was to systematically study how different dark matter models – specifically SIDM and WDM – affect galaxy formation and the structure of dark matter halos when realistic baryonic physics is included. Results. SIDM models tend to produce rounder and more isotropic halos, especially in the inner regions, as a result of momentum exchange between dark matter particles. Group- and cluster-size WDM halos are also slightly more spherical than their CDM counterparts. In all cases, the inclusion of self-consistent baryonic physics makes the central regions of all halos rounder, while still revealing clear distinctions among the various dark matter models, notably the self-interacting ones. Conclusions. The general framework presented in this work, based on the 3D halo shape, can be useful for interpreting multiwavelength data analyses of galaxies and clusters.