7.3 Role of dark matter in structure formation
3 min read•july 22, 2024
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.
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.
The Role of Dark Matter in Cosmic Structure Formation
Role of dark matter in cosmic structures
Top images from around the web for Role of dark matter in cosmic structures
Astronomers Witness a Web of Dark Matter - Universe Today View original
Is this image relevant?
dark matter | UCL Science blog View original
Is this image relevant?
Hubble Provides Most Detailed Dark Matter Map Yet - Universe Today View original
Is this image relevant?
Astronomers Witness a Web of Dark Matter - Universe Today View original
Is this image relevant?
dark matter | UCL Science blog View original
Is this image relevant?
1 of 3
Top images from around the web for Role of dark matter in cosmic structures
Astronomers Witness a Web of Dark Matter - Universe Today View original
Is this image relevant?
dark matter | UCL Science blog View original
Is this image relevant?
Hubble Provides Most Detailed Dark Matter Map Yet - Universe Today View original
Is this image relevant?
Astronomers Witness a Web of Dark Matter - Universe Today View original
Is this image relevant?
dark matter | UCL Science blog View original
Is this image relevant?
1 of 3
- 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 for baryonic matter to collapse and form structures
- Dark matter influences growth of in early universe
- These perturbations eventually evolve into observed (Cosmic Microwave Background anisotropies)
- Dark matter is essential for stability and dynamics of galaxies and clusters
- Helps explain observed rotation curves of galaxies and effects in clusters ()
Dark matter halos for galaxy formation
- 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 ()
- 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 ()
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 ()
- 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 ()
- 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 ()
- These predictions can be compared with observations of galaxy rotation curves and gravitational lensing
Key Terms to Review (26)
Bullet Cluster: The Bullet Cluster refers to a pair of colliding galaxy clusters, officially known as 1E 0657-56, which provides strong evidence for the existence of dark matter. This cosmic collision has created two distinct regions of mass concentration, with the visible matter (galaxies and gas) being separated from the majority of the mass, which is inferred to be dark matter. The observations from the Bullet Cluster challenge alternative theories to dark matter and demonstrate its critical role in structure formation in the universe.
Cold dark matter: Cold dark matter (CDM) is a theoretical form of matter that does not emit or interact with electromagnetic radiation, making it invisible to direct observation. CDM is thought to play a crucial role in the formation and evolution of structures in the universe, influencing everything from the distribution of galaxies to the behavior of cosmic structures over time. Its properties help scientists understand how quantum fluctuations in the early universe can lead to the large-scale structure we observe today.
Cosmic dark ages: The cosmic dark ages refer to a period in the early universe, roughly from 380,000 years to about 1 billion years after the Big Bang, when the universe was mostly dark and devoid of significant sources of light. During this time, the universe cooled enough for neutral hydrogen to form, leading to a lack of luminous objects like stars and galaxies, creating a vast expanse of darkness in the cosmos.
Cosmic filaments: Cosmic filaments are massive, thread-like structures in the universe that serve as the scaffolding for the large-scale structure of the cosmos. These filaments consist primarily of dark matter and gas, connecting galaxy clusters and forming a web-like pattern that shapes the distribution of galaxies across the universe. They are essential to understanding how matter organizes itself under the influence of gravity over cosmic time.
Cosmic microwave background radiation: Cosmic microwave background radiation (CMB) is the afterglow of the Big Bang, consisting of low-energy photons that fill the universe uniformly. This radiation provides a snapshot of the universe when it was just about 380,000 years old, revealing crucial information about its early conditions and supporting the Big Bang model.
Dark Energy Interaction: Dark energy interaction refers to the theoretical processes through which dark energy influences the expansion of the universe and affects cosmic structures. This concept is crucial in understanding how dark energy contributes to the acceleration of the universe's expansion, interacting with matter and radiation in ways that shape the formation and distribution of large-scale structures like galaxies and galaxy clusters.
Dark matter halos: Dark matter halos are large, invisible structures composed primarily of dark matter that surround galaxies and galaxy clusters, providing the necessary gravitational pull to hold visible matter together. These halos play a vital role in shaping the cosmic web, influencing the formation of filaments and sheets while also creating vast voids between them. Understanding dark matter halos helps explain how galaxies form and evolve within the larger structure of the universe.
Density Perturbations: Density perturbations refer to small fluctuations in the density of matter in the early universe, which play a crucial role in the formation of large-scale structures like galaxies and clusters. These tiny deviations from a uniform density distribution emerged during the inflationary epoch and were amplified through gravitational interactions. Understanding these perturbations helps to explain how cosmic structures developed over time and how dark matter influences their formation.
Galaxy clusters: Galaxy clusters are large groups of galaxies bound together by gravity, typically containing dozens to thousands of individual galaxies, along with gas, dust, and dark matter. These clusters are essential for understanding the large-scale structure of the universe, as they serve as key points in the cosmic web and provide insights into the distribution of mass and the effects of dark matter and dark energy.
Gravitational Lensing: Gravitational lensing is the phenomenon where the light from a distant object, such as a galaxy or quasar, is bent around a massive object, like a galaxy cluster, due to the effects of gravity. This bending of light can create multiple images, magnify the brightness of the source, and provide valuable insights into the distribution of mass in the universe, especially dark matter and its role in cosmic structure.
Gravitational potential wells: Gravitational potential wells are regions in space where the gravitational potential energy is lower than that of surrounding areas, creating a 'well' that attracts matter. These wells are crucial for understanding how structures like galaxies form and evolve, as they influence the movement and clustering of matter in the universe. The presence of dark matter significantly enhances the depth and stability of these wells, allowing them to capture regular matter more effectively, which plays a pivotal role in cosmic structure formation.
Harrison-Zel'dovich Spectrum: The Harrison-Zel'dovich spectrum is a theoretical model of the initial density fluctuations in the early universe, characterized by a scale-invariant power spectrum. This means that the amplitude of fluctuations is roughly the same at different scales, which plays a crucial role in understanding how structures like galaxies and galaxy clusters formed from these primordial variations during cosmic evolution.
Hierarchical Clustering Theory: Hierarchical clustering theory is a method used in astrophysics and cosmology to explain the large-scale structure of the universe, suggesting that galaxies and galaxy clusters form through a process of hierarchical aggregation. This theory posits that smaller structures merge over time to create larger ones, with dark matter playing a crucial role in this process by providing the gravitational framework necessary for the accumulation of baryonic matter, leading to the formation of galaxies and clusters.
Jim Peebles: Jim Peebles is a renowned Canadian astrophysicist known for his groundbreaking work in cosmology, particularly regarding the understanding of dark matter and the early universe. His contributions have helped shape modern cosmology, influencing how scientists study the universe's structure and evolution, including the role of dark matter in forming galaxies and cosmic structures.
Lambda cold dark matter model: The lambda cold dark matter (ΛCDM) model is the leading cosmological model that describes the large-scale structure and evolution of the universe. It incorporates the effects of dark energy (represented by the cosmological constant lambda, Λ) and cold dark matter, which together account for the observed phenomena in the universe such as galaxy formation, cosmic expansion, and the cosmic web.
Large-scale structure: Large-scale structure refers to the organization of matter in the universe on scales larger than galaxies, encompassing galaxy clusters, superclusters, and the vast cosmic web of filaments and voids that form the overall architecture of the cosmos. Understanding large-scale structure is essential for comprehending how the universe evolved and the distribution of galaxies over time.
Mass-to-light ratio: The mass-to-light ratio is a measure used in astrophysics that compares the mass of an astronomical object, such as a galaxy or cluster of galaxies, to its total luminosity or light output. This ratio helps astronomers infer the amount of dark matter present, as objects with high mass-to-light ratios indicate more mass than what can be accounted for by visible matter. Understanding this ratio is crucial for exploring the role of dark matter in shaping structures in the universe and for providing evidence of dark matter within galaxies and clusters.
Millennium simulation: The millennium simulation is a large-scale computational model designed to study the formation and evolution of cosmic structures in the universe, particularly focusing on the role of dark matter. This simulation uses advanced algorithms and massive computing power to trace how dark matter influences the distribution of galaxies and other structures over cosmic time. It provides insights into how the universe's large-scale structure developed, showing the importance of dark matter in shaping cosmic architecture.
N-body simulations: n-body simulations are computational models used to simulate the interactions and dynamics of a system containing multiple celestial bodies, often used in cosmology to study large-scale structures of the universe. These simulations allow scientists to analyze how gravity influences the formation and evolution of structures such as galaxies and galaxy clusters, providing insight into the behavior of dark matter and testing various theories of gravity.
Navarro-Frenk-White Profile: The Navarro-Frenk-White (NFW) profile is a mathematical model that describes the density distribution of dark matter in spherical halos, particularly in the context of structure formation in the universe. This profile suggests that the density of dark matter decreases as one moves away from the center of a halo, following a specific power-law behavior that is crucial for understanding the dynamics and formation of cosmic structures.
Non-baryonic matter: Non-baryonic matter refers to forms of matter that do not consist of baryons, which are particles such as protons and neutrons that make up atomic nuclei. This type of matter is significant in cosmology because it includes dark matter, which plays a crucial role in the structure formation of the universe, influencing how galaxies and clusters of galaxies develop over time through its gravitational effects.
Redshift surveys: Redshift surveys are observational studies that map the distribution of galaxies in the universe by measuring their redshifts, which indicate how fast they are moving away from us due to the expansion of the universe. By analyzing these redshifts, astronomers can determine the distance and velocity of galaxies, helping to reveal the large-scale structure of the universe, including cosmic filaments, sheets, and voids, as well as the role of dark matter in structure formation.
Structure Growth Rate: Structure growth rate refers to the rate at which cosmic structures, such as galaxies and galaxy clusters, evolve and grow over time due to gravitational interactions. This concept is crucial for understanding the dynamics of structure formation in the universe, particularly how dark matter influences this process through its gravitational effects, leading to the formation of larger cosmic structures from smaller fluctuations in density.
Vera Rubin: Vera Rubin was an influential American astronomer known for her pioneering work on the rotation curves of galaxies, which provided strong evidence for the existence of dark matter. Her groundbreaking observations revealed that galaxies rotate at such speeds that they would fly apart if only visible matter were present, highlighting the need for unseen mass to account for this phenomenon and shaping our understanding of dark matter's role in the universe.
Warm dark matter: Warm dark matter (WDM) refers to a theoretical form of dark matter that has a mass and temperature between cold dark matter and hot dark matter. It plays a crucial role in structure formation by influencing the growth of cosmic structures such as galaxies and clusters, leading to a more complex understanding of the universe's evolution.
Weak lensing studies: Weak lensing studies refer to the subtle distortion of light from distant galaxies caused by the gravitational influence of intervening mass, primarily dark matter. This effect is measured to understand the distribution of dark matter and its role in the formation of cosmic structures, revealing insights into how galaxies and galaxy clusters evolve over time.