Internal Structure and Environmental Dependence of Subhaloes in AIDA-TNG

This thesis investigates how the structure and abundance of dark-matter subhaloes differ between collisionless cold dark matter (CDM) and velocity-dependent self-interacting dark matter (vSIDM) in the AIDA–TNG cosmological simulation suite. The comparison is performed in both dark-matter-only (DMO) and full-physics hydrodynamical (HYDRO) runs to separate signatures of dark-matter microphysics from those produced by baryonic physics and host environment. The analysis uses structural and demographic diagnostics including the (Rmax, Vmax) relation, stacked dark-matter density and circular-velocity profiles, cumulative radial distributions, and the subhalo mass function (SHMF). The clearest CDM–vSIDM differences are found in the density profiles. In the DMO runs, lower-mass vSIDM subhaloes are generally less centrally dense than their CDM counterparts across the resolved radial range, while the circular-velocity profiles show the same trend with smaller amplitude. By contrast, the (Rmax, Vmax) relation shows only weak and non-monotonic offsets. In HYDRO, the structural trend is not clearly erased, but it becomes harder to isolate because baryons broaden the diversity of the surviving subhalo population. Radial distributions show only weak model dependence, indicating lower sensitivity to CDM–vSIDM differences than internal-structure diagnostics. The SHMF shows a modest low-mass excess of vSIDM relative to CDM for present-day bound-mass selection, but this is difficult to interpret uniquely because baryonic effects, altered stripping, and redistribution between mass bins remain degenerate. Overall, the results indicate that subhalo internal structure is the most sensitive probe of CDM versus vSIDM in this dataset, but baryonic physics, selection effects, and environment must be controlled carefully before such differences can be interpreted as robust signatures of dark-matter microphysics.