substructuresubhalos

Substructuresubhalos refers to smaller, less massive halos of dark matter that orbit within larger dark matter halos. These substructures are a natural consequence of the hierarchical structure formation model, where larger structures are built up from the merger of smaller ones. As a large halo forms and grows, it gravitationally attracts and accretes smaller halos. These smaller halos then become embedded within the larger halo, forming substructures.

The abundance and distribution of substructures are sensitive probes of the nature of dark matter. For example, in the standard Cold Dark Matter (CDM) model, which posits that dark matter particles are slow-moving, a significant number of small substructures are predicted. However, observations of some dwarf galaxies and the distribution of gravitational lensing signals have shown fewer substructures than predicted by CDM, leading to discussions about potential modifications to the CDM model, such as Warm Dark Matter or self-interacting dark matter. The study of substructures involves both theoretical simulations and observational techniques like gravitational lensing and galaxy velocity dispersion measurements. Understanding substructures is crucial for a complete picture of cosmic evolution and the properties of dark matter.