Dark matter plays a crucial role in shaping the universe we see today. It forms a cosmic web, providing the gravitational scaffolding for galaxies and clusters to form and evolve. Without dark matter, the structures we observe wouldn't exist.
Dark matter halos are the building blocks of cosmic structure. They create gravitational wells that attract regular matter, leading to the formation of galaxies and clusters. Understanding dark matter is key to explaining how our universe grew from tiny fluctuations to the complex tapestry we see now.
Role of dark matter in cosmic structures
- Dark matter provides gravitational scaffolding for formation and evolution of cosmic structures
- Forms a cosmic web with filaments and voids (Sloan Great Wall, Bootes Void)
- Galaxies and clusters form within dark matter halos (Milky Way, Virgo Cluster)
- Dark matter halos are sites of structure formation
- Provide gravitational potential wells for baryonic matter to collapse and form structures
- Dark matter influences growth of density perturbations in early universe
- These perturbations eventually evolve into observed large-scale structure (Cosmic Microwave Background anisotropies)
- Dark matter is essential for stability and dynamics of galaxies and clusters
- Helps explain observed rotation curves of galaxies and gravitational lensing effects in clusters (Bullet Cluster)
- Dark matter halos are gravitationally bound structures that form from collapse of dark matter density perturbations
- Gravitational potential wells created by dark matter halos attract baryonic matter
- Baryonic matter (gas and dust) falls into these potential wells
- Infalling baryonic matter undergoes gravitational collapse and forms galaxies and clusters (Milky Way, Andromeda)
- Depth of gravitational potential well determines properties of formed structures
- Deeper potential wells lead to formation of more massive and luminous galaxies and clusters (Coma Cluster)
- Distribution of dark matter halos in universe determines spatial distribution of galaxies and clusters
- Galaxies and clusters are found to reside within dark matter halos (Local Group)
Dark matter in early universe
- In early universe, dark matter played crucial role in growth of density perturbations
- Dark matter is non-baryonic and does not interact with radiation
- Started to form structures earlier than baryonic matter, which was coupled to radiation
- Dark matter density perturbations grew through gravitational instability
- These perturbations attracted more dark matter and baryonic matter, leading to formation of halos
- Growth of dark matter perturbations set stage for formation of first galaxies and stars
- Baryonic matter could collapse into dark matter halos once it decoupled from radiation (Cosmic Dark Ages)
- Power spectrum of dark matter density perturbations determined initial conditions for structure formation
- Shape and amplitude of power spectrum influenced distribution and properties of resulting cosmic structures (Harrison-Zel'dovich spectrum)
Cosmological simulations with dark matter
- Cosmological simulations that include dark matter have been instrumental in understanding structure formation
- These simulations follow evolution of dark matter particles under influence of gravity (N-body simulations)
- Also incorporate baryonic physics (gas dynamics, star formation) to model formation of galaxies and clusters
- Simulations predict formation of a cosmic web with filaments and voids
- Dark matter halos are found at intersections of filaments
- Properties of halos (mass, size) depend on their location within cosmic web
- Simulations reproduce observed statistical properties of large-scale structure
- Predict clustering of galaxies and existence of superclusters and voids (Millennium Simulation)
- Simulated galaxy population matches observed luminosity and mass functions
- Simulations also provide insights into internal structure of dark matter halos
- Predict existence of subhalos and density profiles of halos (Navarro-Frenk-White profile)
- These predictions can be compared with observations of galaxy rotation curves and gravitational lensing