Dark Matter Halos
Dark matter halos are massive, invisible structures of dark matter that surround galaxies and galaxy clusters, providing the gravitational framework for cosmic structure formation.
Dark Matter Halos
Dark matter halos are enormous, roughly spherical distributions of dark matter that form the invisible scaffolding of the cosmic web. These mysterious structures play a fundamental role in both galaxy formation and the large-scale structure of the universe.
Physical Properties
Structure
- Typically follows a NFW profile (Navarro-Frenk-White profile)
- Density decreases with distance from center
- Can extend far beyond visible boundaries of galaxies
- Contains 85-90% of a galaxy's total mass
Formation
Dark matter halos emerge through a process of hierarchical clustering:
- Initial quantum fluctuations in the early universe
- Gravitational collapse of dark matter
- Merging of smaller halos into larger structures
- Continuous accretion of matter
Role in Galaxy Formation
Dark matter halos serve as gravitational wells that:
- Capture and concentrate baryonic matter
- Guide the formation of galaxy clusters
- Influence galaxy morphology
- Shape the distribution of satellite galaxies
Detection Methods
Scientists infer the presence and properties of dark matter halos through:
- gravitational lensing
- galaxy rotation curves
- velocity dispersion measurements
- large-scale structure surveys
Significance
Understanding dark matter halos is crucial for:
- Testing ΛCDM cosmology
- Explaining galaxy evolution
- Mapping the cosmic web
- Constraining dark matter properties
Current Research
Active areas of investigation include:
- Core vs. cusp controversy
- subhalo abundance
- Impact on star formation
- Connection to dark energy
Dark matter halos remain one of the most important and mysterious components of modern cosmological models, bridging the gap between particle physics and large-scale structure formation.