Dark matter halos are invisible, gravitationally dominant structures that surround galaxies and galaxy clusters, providing the scaffolding necessary for their formation and evolution. Composed of non-luminous dark matter, these halos cannot be seen directly, but their presence is inferred from gravitational effects on visible matter, such as galaxy rotation curves, gravitational lensing, and the motion of galaxies within clusters.
Key roles of dark matter halos include:
- Galaxy Formation: Halos create deep gravitational wells that pull in gas from the intergalactic medium, allowing stars and galaxies to form at their centers.
- Structure and Stability: They provide the gravitational backbone that keeps galaxies and clusters bound despite their rotation and interactions.
- Merger Histories: Halo interactions and mergers drive galaxy growth, star formation, and the assembly of large-scale structures like groups and clusters.
Observational and simulation studies of dark matter halos help astronomers:
- Map the distribution of dark matter in the universe.
- Understand galaxy formation and evolution within a cosmological context.
- Explore the cosmic web, since halos trace the filaments connecting galaxies and clusters.
In essence, dark matter halos act as the invisible framework of the universe, shaping the formation, dynamics, and evolution of galaxies across cosmic time.